"A fantasy d20-themed dungeon crawler", to quote DarkGod's comment. Inspired by Incursion by Julian Mensch. Made available under Open Game License. This is a non-profit fan project. No money is made. There are currently only two people working on the mod. However, we have released several beta versions so far.
... well, read a book to improve your stats, in any case! There's one for every attribute under the sun (except Luck), in one of five flavors, from one to five!
Be warned though, they only drop when the level is very high - that is, deep in the dungeon.