One book that simply covers the basics of design is Idea Index: Graphic Effects and Typographic Treatments by Jim Krause. It's a fun pocket sized book that makes for easy travel if you are in school and covers simple type treatments.
A book that I was assigned in school was Orbiting the Giant Hairball by Gordon Mackenzie. It is a great little book that can help you get out of creative funks. It kind of helps you remember to think outside the box and not get weighed down by your projects.
Some other books that I was assigned in school were type specific. And boy do I need help in that area, to this day. Any designer knows that type is extremely important to any design and it is not something to glaze over. So far as I am concerned the more you can learn about it, the better. A couple of books for type are: Thinking With Type by Ellen Upton and Making and Breaking the Grid by Timothy Samara.
In the realm of type, but more along the lines of inspiration rather than instruction are Just My Type by Simon Garfield and Typography Sketchbook by Steven Heller. The latter I actually just got for the BF and it is AWESOME. I had half a mind to keep it for myself, but it has some really awesome images for inspiration.
In terms of general inspiration a great one that was given to me was Everything That Can Happen in a Day by David Horvitz. This one is not so much solely graphic design inspiration, but general creative/think about things in a new way kind of inspiration. It's an all around a fun book, so definitely recommend picking that one up.
I also subscribe to Graphic Design USA, which is a nice way to keep up on trends and things happening in the industry. Plus a bonus is, if you are in the industry, they send you a subscription for free, so can't beat that.