I call myself a slightly above average gamer. I played AD&D 2.0, 'cause we had nothing else. I've played a few White Wolf systems. Even played the old Star Wars d6 game. Currently, I do stuff with 7th Sea (d10), the new World of Darkness systems, and a D&D 3.0 game.
D&D 3.0 and 3.5, and d20 in general, leave a bad taste in my mouth. I don't like class systems, leveling systems, XP you can't spend. And d20 is all of these. Granted, it made 3.0 years better than 2.0 (and the God-awful 2.5). But still...
Then I read Grimm. Grimm is a short book, just 62 pages, and uses the d20 Open Game Licence. But it is so much better than any other d20 that I've ever seen.
The Grimm Lands were created when the Grimm Brothers in our world created records and stories of the nightmares and fantasies that exist, and by chronicling them, banished them to anyother place. Here, the fairy tales became twisted and evil. Cinderella is a slaver, Rapunzel a hollow husk controlled by the spiders of her tower, Red Riding Hood a vampire, and much more. The land is ruled by a very insane Humpty Dumpty, who lost his mind upon falling off his wall.
Into the twisted (but clearly justified) world, children from our world can sometimes fall, fueled by the imagination of the young age. And this is where the players come in.
You play children, between ages 8 and 12, who find themselves trapped in the Grimm Lands, desperately searching for a way home. Hopefully, you'll find one, or find a new reason to exist in the Grimm Lands.
New feats and skills have been added to the d20 core rules; others are merely revisions. For example, the skills Survival and Heal from d20 have been lumped together into the new skill Boy Scout Stuff.
But the most endearing part is the new character classes, seven in all. They are the Bully, the Dreamer, the Jock, the Nerd, the Normal Kid, the Outcast, and the Popular Kid, each with ther own brand new powers, strangths, and weaknesses. They are too intricate to go into here, but I assure you they are amazing.
But what really sets this apart from most d20 games (besides the amazing classes, world set-up, and underlining charm of everything) is the leveling system. The rules suggest that you don't give XP to the players; instead, at the end of every game, everyone just goes up one level. Each character class has but six levels, and the rules suggest that you should never run a story for more than six games. This kills all munchkin options; no ore "Look what my character can do now!" and no more "We must kill everything so we can level faster." Pure and simple gaming for the sake of gaming, and it's a pleasure with everything they've loaded this book with.
Get the game, and amaze yourself. This is something no one who does RPGs should miss out on.