I'm always interested in books on writing and becoming a better writer. It's easier to read books on writing than to write, but the question is still worth asking...
What are your Big 5 books on writing?
These should be books written with the intent of teaching you to write. I know other books can help you be a better writer (including books about writers), but let's stick to your favorites on the art and craft of writing. It can be about fiction or non-fiction writing. It can be about poetry, articles, essays, letter writing, or most anything else. This is not a list of books on how to write a sermon. Feel free to throw one or two in there on grammar issues or issues directly related to writing if you like. If you don't have 5, no prob. List what you have read that you like.