I got the book The Creative Writer's Style Guide by Christopher T. Leland the other day. It is a style guide much like The Chicago Manual of Style or The Gregg Reference Manual but this one is focused on creative writing not business styles. The best part was that B&N had it in the bargain books for only $6. It is definitely worth that, and if you don't have another good reference this is a good one to start with, even at full price.

It starts with a section on parts of speech, for those of us who slept through high school english, goes on to sentence structure, punctuation, and a whole chapter on dialogue. The second section is about style.