The only book I know of specifically directed at IDPA is
Practically Speaking, the Game, Guns, and Gear of the International Defensive Pistol Association
by Walt Rauch (IDPA Director & cofounder)
http://www.eastontacticalops.com/rauch/index.html
It is a slim little thing but should give you some guidance on how to apply what you have learnt about shooting in general.
You ARE shooting in addition to reading, aren't you?