Okay, seriously, hear me out. This is a good game!
Yeah, sometimes it is safe to judge a book by its cover. This is one of those cases. This looks like a kid's game, and it very much is. And as a kid's game it rocks. But for the reasons it excels as a kid's game, it has great potential for us older gamers too.
Premise and Setting: You play some type of merfolk, an intelligent aquatic creature that swims around and does... stuff. What stuff? All kinds of stuff. There's not much of a firm setting here, really. No overarching metaplot or storyline, no war you're drafted into or anything. You have a history and society section for the merfolk, and list of enemies like sea witches and (my favorite) the Kraken, but it's up to you to do something with it. And this is a strength, I think, as kids probably ain't having all that anyway. You're free to do whatever. The Navigator (GM) can choose the adventure or roll randomly for it, easy enough that kids can run this game as well as play it. Big selling point.
Character Options: You have a range of interesting and appealing "folk" racial types, each a hybrid of humanoid and a species of sea animal -- fishfolk, octofolk, sharkfolk, even jellyfolk and urchinfolk -- with unique strengths and weaknesses. You have no class setup, though each player picks four unique qualities (in addition the ones granted by type) to customize their characters. This way, you can play a warrior-type, magic-user or pretty much whatever suits your fancy.
Rules: Mermaid Adventures uses the PIP System. It's simple, as you might expect, but good. You need a number of six-sided dice of two colors; the book refers to white dice and black dice, but there's no good reason you can't use other colors as long as you designate which ones function as "white" or "black." You form a dice pool from the white dice based on your character's attributes (Body, Charm, Luck and Mind); one die in a stat is poor while five dice is awesome, not unlike White Wolf in this regard. As you roll your white dice pool, you simultaneously roll a number of black dice based on the difficulty of the task, with more black dice indicating greater difficulty. (This means all the rolls are made by the player when she has her character act, instead of rolling against the Navigator.) Each result of 4, 5 or 6 on any die is a success. Now you compare successes: More white successes means you succeed, more black successes mean you fail. The more (white) successes fr you the better. Easy-peasy.
Conflicts are interesting. When two characters face off, the attacker/acting character rolls her attribute dice (white) against the defender's attribute dice (black), per the rules above. The attacker determines what attribute she rolls based on the sort of conflict she's initiating, while the defender usually (though not always) defends with the same attribute:
Body: Hit you (attacking)/dodge you (defending)
Charm: Persuade you (attacking)/assert will (defending)
Mental: Trick or outsmart you (attacking or defending)
Luck: Use magic (attacking)/resist magic (defending)
Rather than a general health/hit point pool, characters take "hits" to the defending attribute. Falling to zero hits can result in different things, depending on the attribute: Stun (Body), headaches (Mental), lose voice (Charm), or bad luck (Luck). This I like a lot.
Aesthetics: Mermaid adventures is a small and compact 6" X 9" book, its rules and three adventures fitting in under 100 pages. An easy fit on any shelf. I have the color version of Mermaid Adventures, and the book is a delight to look at. The artwork is beautiful; the colors are bright and crisp, and there are several full-page pieces. You get a very clear idea of what the various merfolk types look like. The tables throughout the book are a nice shade of cyan, though I think are a bit blocky and plain-looking and could probably be prettier. But they serve their function.
Flaws: None to speak of, really. I mean, there is the occasional editing snafu, but nothing egregious enough for me to drop my Style assessment from a 5. The simplicity of the Mermaid Adventures system, and its fanciful tone and premise, may not be everyone's cup of tea. It is aimed at a younger audience after all. So if you're extremely serious and grimdark then this isn't the game for you I'm afraid. But if you're not afraid to loosen up have some casual fun, then you will like this game.
In Closing: While Mermaid Adventures is a game you can enjoy with young family members when you're not playing with your normal group, I reiterate how the game has fun potential for us adults too. The rules are "lite" and quick, and are transparent enough that you can add your own rules and stuff with little fuss. Want to add new merfolk types, like dolphinfolk or crabfolk? New equipment? New magic spells? Not difficult at all.
I've actually considered more extensive mods, roughing up the game and making it more serious. I have a skill system in mind to plug into the game, even ideas for implants, rules for mutations/evolution, and psionics. (Yes, this is bad and awful and kills its happy, but if I'm running it for adults I'm allowed to do that.) The PIP System can be adapted to low-level supers setting or serious fantasy, whether you want to keep the mermaid elements or not. The game author doubtlessly has other settings in mind for this system.
So yeah, buy Mermaid Adventures. Your kids will love you for it, and even if you don't have any, I'm confident you'll like the game unless you're just trying to be a curmudgeon.