Books about the creative process (finding the courage to write, getting ideas, fooling around with them, etc):

Writing Down the Bones, by Natalie Goldberg

Bird by Bird, by Anne Lamotte

Writing Without Teachers, by Peter Elbow

The Elements of Invention, by Jeanne H. Simpson

Books about writing craft (structure, organization, sentences, audience, plot, etc):

The St Martin’s Guide To Writing (NOT the St. Martin’s handbook)

Can I Change Your Mind, by Lindsay Camp

Self-Editing for Fiction Writers, by Renni Browne and Dave King