I read the BPL lightweight backpacking book which can be found on this site, first. It's fairly informative and will get you on the track of thinking in a lightweight way towards your gear and methods.
The lighten up book was one of the next books I read. It's a great book, but if you are looking for a book that covers basic backpacking techniques for a beginner it lacks a little, but is an excellent supplement to add even more knowledge and a few more ideas towards what can be done to lighten up.
Then the 3rd book I read which filled in even more gaps of things I've pondered is, Trail Life by Ray Jardine. Some will criticize some of his methods or methodology, but if you take the "full of himself" rhetoric aside and analyze the techniques used you can gain a lot of information. There's a little of everything covering how ray approaches the majority of stuff you'll come across in the wilderness.
These are the 3 books that really started me along the path to gaining my lightweight techniques and started me backpacking on my own.
Careful who you ask stuff to at REI, and take it with a grain of salt especially if you want to go lightweight or ultralight. Some stores have some good personal that are knowledgeable towards the light side, but others I've talked to have tried to talk me or my girlfriend towards a heavier pack or other gear. Since I was empowered with knowledge, it was easier to resist the 5 pound packs.
First and foremost though the reading will only get you so far. You'll have to get out and find out what works the best for you, or which of the techniques you can tweak to fit your clime and style. Trial and error has been the best confidence builder with my backpacking over the last several years.