Can anyone suggest some good art books? I'm talking anything from anatomy, to poses to light and shadow studies.

I'm basically looking for how-to books in general that help you improve whether it be with special exercises or teaching techniques. It doesn't matter if it's for realistic or cartoony art and both beginner and professional books are fine.

I'm seriously looking to step up my game a bit this year and I feel studying and getting a few pointers might help.