I just finished reading that book mentioned above by Mr Petersen, which I signed off the public library. It's aimed at real beginners, but I found it an easy read and, by approaching it with a humble disposition, I was able to learn a number of things that even at my stage I didn't know. (Now, when I say 'my stage' I'm not saying I'm a top shot, but I'm shooting professionaly, which is mighty scary considering my deficiencies. Ah, well, some of us only learn to swim by jumping into the water: it's swim or drown.)
I'd recommend getting Mr Peterson's book Learning to See Creatively. I signed it off too and am currently working on it. It's an easier read than Freeman Patterson's Photography and the Art of Seeing which is very good, but denser. Yet, another one for your library.
I've also learned a lot from Michael Freeman's books. Do get The Photographer's Eye (just the part on composition will pay for the book once you translate it into successful pictures), The Photographer's Mind, and Perfect Exposure.
Finally, do buy Light - Science and Magic by Hunter, Biver and Fuqua. A must-have textbook for lighting.
I guess all that I listed might exceed your budget. Get Light - Science and Magic, and either Learning to See Creatively or The Photographer's Eye. I think the former is out of print and no longer stocked by Amazon, but the sellers have copies, even new ones; otherwise, get Michael Freeman's.
Avoid buying books with 'techniques' which are nothing but kitchen recipes that work in particular cases (i.e. in situations identical or very, very similar to those portrayed) or that rely on software programs/features that can become obsolete pretty quickly. Opt instead for getting the foundations down, then you can tackle any assignment and develop your own techniques.
