I've been hanging out at the library quite a bit recently. There are some really incredible books on design out there. Here are a few I've picked up recently.
Before & After: How to Design Cool Stuff by John McWade
Seriously, this book blows my mind. It is probably the best design practical overview I've ever seen. It reads much like a textbook, and the lessons are so down to earth—almost scientific in their approach. The way in which basic design principles are explained is so simple and yet so groundbreaking. Pretty sure I'll end up buying this book in the near future, it's that good.
Graphics Explained by Michael Evamy
If you really want to be a design geek, you have to read this book. It's like reading a scientific journal of medicine, but for graphic designers. Basically a collection of case studies, this book shows how design firms work with clients, approach briefs, and develop concepts. It's really interesting how diverse the approaches are. What amazes me the most, though, is that somehow, even the most methodological process has a big element of serendipity. That shouldn't surprise me—it is art, after all. ;-)
Creative Workshop by David Sherwin
I found this book while looking for books with creative prompts or something similar. This book is basically like an advanced graphic design course—80 imaginary design briefs to work on with time limits and guidelines. They include things like magazine covers, logo design, type layout, etc. Really cool book. My favorite part is the "randomizer"—various kinks you can cut out and pull out of a hat halfway through an exercise (like "make the logo bigger" or other random things that really do actually come up when you're working on stuff for a client) to shake things up a little and force you to think on your feet. Really fun, useful little book!