I’m using this book having come highly recomended. It takes you setting for Bridge, ACR and PS. Global adjustments in ACR and pretty much everything you need in PS. I like it because its one of the few books written for an by Nature Photographers. I find most books, includingthe ones by Scott Kelby ( good book all the same) to include too much information thats not applicabe or rarely used because it targets a broad audience.
http://www.amazon.com/Photoshop-CS3-Nature-Photographers-Workshop/dp/0470119896
Its an option if you want one thats targetted for the type of photography we would do. If you want the Cornucopia type than certainly Scot Kelbys would at he top.
/edit because its way too ealy in the am and my brains functioning faster than my fingers type, omitting entire words 🙂