If you need to figure out why your are compelled to do this crazy thing called writing and need some gentle encouragement (or psychoanalysis), read:
Writing Down the Bones, by Natalie Goldberg
Art & Fear, by David Bayles & Ted Orland
If you need some good old fashioned technical direction, read:
Self-editing for Fiction Writers, by Renni Browne & Dave King
The Elements of Style, by William Strunk and E.B. White
If you are looking for ways to build a novel, read:
Scene & Structure, by Jack M. Bickham
Hooked, by Les Edgerton
If you want some good advice on craft, read:
Bird by Bird, by Anne Lamott
On Writing, by Stephen King
Old Friend from Far Away, by Natalie Goldberg
642 Things to Write About, by the San Francisco Writers' Grotto
The Nice Thing About Strangers, by Paige M.J. Erickson