The writer makes no bones about the fact that the whole point of this game is to be a drunken violent lout that performs drunkenly violent acts of heroism, sort of in the vein of the Conan cartoon from the '90s. There are even green scaly lizard-creatures, though in Barbarian Versus they're aliens instead of demonic wossits from another dimension. This is one of the few games I can remember finding that flat-out says, "This is what this game is about, this is what the rules support, this is the theme that fits the rest of it." That sort of thing automatically gets support from me, since I'm a wee bit tired of games that claim to be about everything and nothing at the same time. Schrödinger's RPG this ain't.
The setting is a place called the Northlands in faux-medieval time that has just been invaded by reptilian space aliens with a bunch of weird gadgets. Most of the rest of the .pdf that makes up this game is devoted to creating barbarians and killing things with them. There is no canon list of barbarian clans or groups, which is also a welcome shift from certain games that shall not be named where you can only be an X, a Y or a Z if you want to fit in. This makes for easy character creation without the hassle of playing something that doesn't fall exactly into predefined requirements. In theory, a GM that wants to play a protracted or political campaign of Barbarian Versus will probably find this very difficult, since there's no backstory for how the Broken Tooth Clan and the Purple Ear Clan had a war over economic concerns back during the reign of Muglug the Flatulent. Then again, since the cover art is two guys in loincloths with axes facing down a great big lizard from space, somehow I can't feel sorry for that theoretical GM.
After a clan is picked, points are assigned to Feet, Craftiness, Contemplation, Smash, and Throw. There are also points for different abilities and items, and some elementary mathematics for figuring out how many injuries the character can take before dying - the Guts stat - and how much luck the character has - the Grit stat. Grit represents a pool of extra dice the character can use when necessary - each point is one die.
There are also sections devoted to what the barbarian cares about and is afraid of. Depending on whether one wants to play a fairly serious game or a comedic Groo-style one, the things cared about could be Saving Helga From The Aliens, or Stealing The World's Largest False Nose. The barbarian is also required to have a war cry - ideally something punchy. Some extra tidbits can be added to the character if the player likes.
The only times dice are explicitly required in this game are when the barbarian is doing something dangerous or heroic. I particularly like this bit, since I'm one of those people who could crap out with loaded dice. The writer emphasizes the importance of describing what the barbarian is doing - particularly amusing or interesting images can gain extra dice at the GM's discretion. It's also possible to be penalized dice for lackadaisical participation from the player, bad equipment or running into something the barbarian is afraid of.
Since this game is unashamedly about bashing heads, which is a welcome switch from games that really are but pretend not to be*, the biggest single section of the rules is devoted to fighting. Combat is mainly short and brutal - slide rules and high geometry not included. At the end of each session or adventure, the characters earn Fame and Fortune points, which are pretty much what they sound like. They can be used to buy up different stats and replace used Grit points. Fame and Fortune also don't carry over from session to session, so there's no hoarding. Also, characters that survive will slowly accumulate Legend points - the character with the most Fame and Fortune at the end of each session gets a Legend point. Once the character has five, he or she becomes a Legend and basically retires to become chief of a clan or something like that.
The GM section is standard as GM sections go - advice on how to create the space aliens, plots, story ideas, and the Random Looting Table. The biggest section of rules outside of the Rules section, which is unsurprisingly the Drinking section, appears here. There are some ready-to-use characters and an included adventure.
I've had this lying around on my hard drive since my Internet connection last year, and I regret not looking at it sooner. Personally I don't know if I'd play a Barbarians Against Green Aliens game, because I'm thinking that with a minimum of hassle it could be converted into the Discworld Hero game, where the characters follow in the footsteps of Cohen the Barbarian. With a bit more tweaking it could also easily turn into the Thundarr the Barbarian game - there might need to be one or two more charts on the Random Looting Table, though. There's even a section devoted to different ideas to use with this game - considering that creating NPC enemies is profoundly easy it shouldn't be difficult, compared to games that require six forms and a pint of ink before one NPC is done. This is very easy to read and is well laid-out, with few sidebars and no bizarre pictures that the text nonsensically surrounds. The character sheet also has a great big axe on it, which is a plus in this sort of game. This is not particularly serious, but as a non-serious game it succeeds smashingly.
* I know I've said this once, but I felt it was important enough to be worth mentioning again.

