One of the books that I read way back in the day (and still sometimes consult) that was quite a good overview of Homebrewing, both extract and all grain, is Dave Miller's Homebrewing guide. This book is quite good in getting into the science involved in mashing, boiling, fermentation, etc. but doesn't get more complex than is really necessary for a intermediate brewer. I do feel that it is not laid out very well (you kinda have to search back and forth through chapters to formulate the information that is pertinent to your situation) but is certainly was a great book for me.
Charlie Papazian's The Complete Joy to Homebrewing is considered by most homebrewers as " the bible" and definitely has great information in it as well. He does delve into the science of brewing as well, but I feel that he writes in a more "flowery" manner than Dave Miller who tends to be a bit drier in his writing technique.
If you are looking for books on recipe formulation and don't mind technical writing, Ray Daniels Designing Great Beers is a good book to go through (I am actually reading it right now).
PS if you live in Denver, I know that the public library has both "The complete joy of homebrewing" (although an older version) and "Designing Great Beers"
Hope this information is of help!