This is the book to start with. This explains the ins and outs of exposure and is definitely the one to take out with your camera. He gives you great challenges and assignments to try. If you only have time to read one, read this one:
These next two both offer a lot of advice and inspiration. He has a way of making photography exciting again for me. I can't say enough!
Head to your local library and put these on hold, or better yet - head to the bookstore, get a hot chocolate, whip out your bank card, and enjoy!