I can't beat Nigel's review for brevity, although I agree with him, more or less. In being a litte more verbose, I'll hopefully be able to explain what led me to the same conclusions.
I have never played, or even seen, the Twilight Imperium board game. Largely from its reviews I gather that it is an excellent strategic-economical simulation game of galactic conquest with elements of Cosmic Encounter (abilities special to "races"), Civilization (trading, advancing science and technology), Diplomacy and Risk (moving crowds of markers or miniatures across the board to bash the other players' armies). Twilight Imperium The Role-Playing Game is role-playing in the same setting.
The problem should be obvious: What appeals to the board gamer doesn't necessarily appeal to the role-player as well. The board gamer wants clear distinctions between the game elements, e.g. the player races, otherwise why bother with making a distinction at all. This means each race is a monolithic, uniform bloc, a trader race, a fighter race, a scientist race, etc. To any self-respecting science-fiction role-player, however, Lucasisms like this are an abomination. The role-player wants a rich background, with detailed descriptions and subtle niches to fit in the characters. But if the authors had expanded the board-game setting to such an extent, it would have been unrecognisable to the (probably) intended audience, the Twilight Imperium board gamers.
Another matter is power. In the board game, I assume, you play the dictator of your markers' colour. In a role-playing game, you almost never (and definitely not in Twilight Imperium The Role-Playing Game) play the top echelon decision-makers. Your players' actions might have tremendous effects, but you generally can't order up a squadron of dreadnaughts to reduce a planet to slag. Han Solo's contribution to the Rebellion in the first Star Wars was crucial, but he still was a lowly tramp freighter captain.
Because Twilight Imperium The Role-Playing Game is the RP-ization of a board game, its intended audience is not only the science-fiction role-players, but also the Twilight Imperium board gamers. In the following I'll try to show why it will disappoint both groups.
Stereotypes, clichés and conventions
The authors see three defining elements in a space opera: a cinematic plot with larger-than-life characters who regularly save the universe; the lack of consistent pseudo-science, i.e. the sf gadgets are there to support the plot and need not be explained even in the hypothetical frame of the setting; and a clear-cut morality of good versus bad. Twilight Imperium The Role-Playing Game is a "political space opera", which does away with the third element. This isn't really surprising; the six Great Races open to the players (board or game) compete for the same resources, so what harms one benefits the others, and there is no black hat race for all to gang up on.
Apart from that, the Twilight Imperium The Role-Playing Game background is entirely conventional. I'd say it is the most stereotypical game I have ever seen, and it looks like it, along with its mother game Twilight Imperium, was designed to be so. We have the trader, fighter, pilot, diplomat and scientist races of feline, insectoid, drow, saurian and grey descent and the possibly even more stereotypical non-stereotypical Humans, who rely on their diversity; the Lazax precursor race (and mildly weird alien names); lost planets, a guardian race; jump drives; wormholes; planets with a single climate zone, a single culture and uniform appearance; macguffin chemical elements like Star Trek's dilithium or Babylon 5's quantium-40; and so on. This is probably ok for a board game, where the players want to concentrate on the resources available to them without being distracted by background sugar coating. This might even be ok for a RPG, too, to provide the players with a familiar baseline, if there were a few new ideas. Unfortunately, the setting of Twilight Imperium The Role-Playing Game has no original ideas at all.
Vague and bad prose
The authors might have gotten a few new ideas if they had produced a little more text, had probed the depths of the setting. Sadly, they just skim over the topics, drop a few names from the board game and close the gaps in between with lame and vague putty sentences. The whole book reads like a bad freshman term paper. It gives a general overview without showing or promoting a deeper understanding of the matter, occasionally tries to deceive the reader into thinking the opposite and fills up the page count with meaningless phrases.
For example, there is an 11-line paragraph on page 44 describing the human life-cycle. The best thing I can say about it is that the authors tried to be cute but failed. The information given is superfluous, and it is a ridiculous attempt at a neutral point of view. I want a role-playing game written by human authors, not by people who think they need to disguise themselves as in-game aliens.
The prose sometimes drops to mindboggling stupidity. Take the first sentence of the skill description for throwing (p. 58): "The known universe is full of objects for characters to throw." No book is a good read if you regularly have to get up and bang your head against the wall to make the pain stop!
Most annoying about Twilight Imperium The Role-Playing Game is its vagueness. P. 94: "The Narrator's job description could fill several pages but can be condensed to a few basic concepts." It is, in the next paragraph. Fifteen (15) lines! Fifteen lines of text so general it becomes meaningless. And the rest of the "Narrator's Guide" isn't much better. On occasion, the authors tell the GM what he or she ought to do, but they never, ever tell him or her how to do it. For example, the authors make a big point about Twilight Imperium The Role-Playing Game being "political space opera", probably because the game has no other distinguishing feature. But they support the GM in that aspect with just four short paragraphs culminating in a sales pitch. Among meaningless drivel like "Politics keeps the game's setting interesting and fresh" or flogged-dead phrases as "wheels within wheels" all the authors do is try to convince the prospective Narrator to do politics. No hints on how to accomplish it, no rules how to manage power blocs, no examples how to involve the player in the universe-spanning struggle, no help whatsoever.
In my opinion, all the vagueness of the descriptions, all this hinting at information that isn't given has a taunting or teasing undertone: It reads like the author could have supplied all the facts and rules missing from Twilight Imperium The Role-Playing Game if they wanted to, but they didn't care enough about their audience. I admit, this is highly speculative, nevertheless it is the impression that the larger part of Twilight Imperium The Role-Playing Game gave me.
Doesn't support the GM
If the section about politics is no help to the GM, the chapters "Technology" and "Space Travel" are no better. Aside from the usual shopping list, all "Technology" does is dropping a few names in a bad attempt to tie the role-playing game to the Twilight Imperium universe. The paragraph on the "XRD Star Class Transporter", for instance, reeks of the board game. Chances are slim that the players, or even the GM, will more than random encounter it. What is especially sad about it is that I expect the "XRD Star Class Transporter" to be some nifty playing-piece in the board game, while in the role-playing game it is such a dud. If I were a Twilight Imperium board gamer trying out the RPG, I'd feel disappointed.
"Space Travel" tells us on p. 87 that "There are dozens of in-system drives available (each shipyard has at least three different models), each with its own strengths and weaknesses." but never gives the reader so much as a single engine, with or without strengths or weaknesses. The only advice on in-system engines is that the faster they go, the more expensive they are. Hey, who would have thought of that?!
The paragraphs on the economics of space travel are particularly annoying. After quoting a price for a day's worth of transportation, all in a verbal cloud, it goes on to PC-controlled spaceships. You will note that I didn't say PC-owned, because player characters cannot have their own ship. They may, for some reason, have the use of a spaceship, but they bloody well can't be its rightful owners. This may be alright in character creation; after all, a spaceship is a big investment and if you handed them out for free to any enterprising player who wrote "owns a big spaceship" in the character concept, everybody would want to have one. So it's ok if the PCs are up to their eyeballs in debt so that they can share a ship among them before the campaign starts. But the book doesn't provide them with a way out of it. There are no data to compute repayment, no rules for economic complications, heck, the few sample ships present in Twilight Imperium The Role-Playing Game don't even have a price-tag, so they will never even know how much "up to their eyeballs in debt" means in the first place. The whole section is just a badly disguised game-management device: The PCs can only have a ship if they explicitly give the GM a means to screw them. This rare example of providing the GM a handle for the game is so ham-fisted as to be unusable.
The player group won't work
One of the crunchy bits of speculative fiction RPGs is that you can play non-humans. It's cool to have a party with a miniature viking fighter, a shield-surfing hairdresser with a submachine bow and a lazy hairy-footed thief. Twilight Imperium The Role-Playing Game provides the same, I guess, six player races as the board game, the Hacan trader cat-people, the reptilian diplomat Xxcha, the brutal insectoid N'orr, the semi-aquatic egghead Hylar, the ruthless pilot Letnev and the boringly diverse Humanity. Cool. However, since the races have particular affinities and prejudices about the others and they are pitched against each other (and not against the Orcs, Klingons or whatever the GM's bad-guy race is), maintaining party cohesion will be no end of fun for the GM. Another legacy of the board game.
The obvious way to get over this obstacle would be to divide the Great Races in player and non-player races and pitch the PCs group against varying coalitions of members of the NPC-races. But doing so would destroy the feel of the Twilight Imperium board game, with its Diplomacy-like shifting alliances and political backstabbing.
The authors even see the problem (p. 97), but their lame excuse for a solution is for the GM to tell the players to go and create characters who function as a group. Great!
Interesting character representation
There are three good things about Twilight Imperium The Role-Playing Game, all, sadly, of rather limited significance. One is the character representation. Superficially, Twilight Imperium The Role-Playing Game looks like another attribute-skill-system. Unlike other systems, however, which have "natural" attributes like "Strength", "Dexterity" or "Intellect", and base their skills either on attributes which don't quite fit or on elaborate computations involving several attribute values, divisions, square roots and logarithms, Twilight Imperium The Role-Playing Game puts all the 57 skills in five buckets and invents label attributes (called statistics) for them. This means "Strength" is a skill, the chance to perform some feat involving muscle power, based on "Body", which represents a character's ability to acquire and handle skills like Strength, Stamina or Swimming.
The advantage of this system becomes more pronounced with the soft skills, which not quite fit dexterity, intelligence, wisdom or other traditional attributes. Twilight Imperium The Role-Playing Game's other four "statistics" are Charisma, Mind, Education and Ability, the most interesting of which are the last two. Education reflects the character's ability to acquire theoretical knowledge, things you have to go to school or college for like Surgery or Dreadnaught Piloting, while Ability is for skills that come with practice, like Melee Combat, Hide, but also Streetwise! This is an ingenious approach, even if the association of some of the skills to their base attributes, e.g. Teaching to Ability, is debatable.
Smooth rules system
The rules are fairly simple. There is just one mechanism, the "skill roll". Add the required skill (in the range 0–60) to the attribute it is based on (1–20) to get a percent chance to succeed (it the GM feels like it, he or she may add or subtract a few modifiers). The mechanism isn't very cinematic; even a minmaxed character still has a 20 percent chance to fail at his specialty task. The rules when to apply the mechanism try to counter that effect; if a character has a skill value of 30, he or she doesn't need to roll to use it if the situation isn't critical in some way. This means the game-play won't bog down in die-rolling each time the party decides to walk across the room.
Two pages of general rules are followed by four pages of combat rules. These, however, are just applications of the same mechanism with a few bells and whistles like initiative or the effects of armour. Nevertheless, the combat system might come as a surprise. There are just three (personal) combat skills: unarmed, using melee, and distance weapons. The weapons do not add modifiers to the to-hit roll (a few have special damage rules). Range is optional, as is cover. The amount of damage is fixed, it is either dependent on the Body attribute (unarmed), the weapon used (distance weapons) or both (melee weapons). This is probably unrealistic as hell but I find it rather elegant. Combat is bloody deadly (haw, haw), the average character has 58 hit points and will be down after a single hit from a rifle-type weapon, two or three handgun hits and likely be cut apart by an opponent wielding one of the heavier edged weapons. All this because there are no saving-rolls. The only way to escape damage is dodging successfully, and dodging means the character can't do anything else in that round.
Six pages of rules (and another few pages for starship combat and the like) obviously don't cover every contingency — or even most contingencies. In fact, there are a number of obvious mistakes (e.g. 5×8=45, p. 50) and questions remaining, e.g. if you can raise a skill over 60 points with experience. This isn't too bad, though. If you want a rules-light system, you'll always need to do more interpreting.
Optics
This is probably why I fell in love with Twilight Imperium The Role-Playing Game about five years ago. At that time I had the good fortune of being too broke to pay the, say, 40 D-Mäcs. But Twilight Imperium The Role-Playing Game sure looks good, in that understated way that no longer sells role-playing products these days. The layout is clear, the headings obvious, the tables and example boxes have a pleasant shade of gray that lifts them out of the surrounding text without rendering unreadable what's inside. The "watermark" background images are few and far between, and they are unobtrusive enough not to distract from reading what's printed on top of them.
The illustrations aren't exactly Picasso-grade. They are black and white (with the obvious exception of the cover), have a few subtle mistakes (just look where the girl's knees are on p. 5!), but blend in with the rest of the book. Twilight Imperium The Role-Playing Game's presentation is GURPS done right, GURPS without that congested look (and sidebars). Just opening the books brings back the mid-1990es, the peak of black and white role-playing books before the attack of the four-colour glossies. Only Twilight Imperium The Role-Playing Game was published in 1999.
Summary
The three nice or interesting aspects of Twilight Imperium The Role-Playing Game can't make good its many failings, though. The rules might appeal to lazybones like me, but there are enough other rules-light systems out there. The old d6 Star Wars isn't exactly rocket science either. As a background, Twilight Imperium The Role-Playing Game is both too unspecific and too conventional to use. Just get GURPS Space and roll your own (and if it's Cherryh's Compact-Union/Alliance universe, I want a copy!). The antagonistic nature of the player races will probably cause enough friction not to make the game worthwhile. So much for role-players.
For the board gamers, Twilight Imperium The Role-Playing Game doesn't offer the clarity of the board game, cuts your player characters down from dictators to nobodies and rubs salt in the wounds by flashing interesting (I hope) concepts of the board game that will forever be unattainable to the lowly PCs.
Or, as Nigel said,
