While I can't really recommend any books, I will say that you should just practice, practice, practice. I love graphite and it's a really awesome media but it does take time to learn.
Just sit down and draw from life. It's much easier to grasp the idea of line and form in 3D than staring at a picture, and I feel that you'll take a lot more from it than just simply re-drawing from a photo if you're still learning and building your foundation.
But that's just my opinion. :)