I must confess I don't use many books about writing as much as I read books with good writing. However, the books about writing I use most are The Elements of Style by William I. Strunk, Jr, and E.B. White, The Elements of Grammar by Margaret Shertzer and Learning Grammar Through Writing by Sandra M. Bell and James I. Wheeler.
I like reading Jane Austen, E.B. White, Dr. Seuss, Charles Dickens, Mark Twain, Charlotte Bronte, Shakespeare and many other good writers. I think it is true that reading lots of good writing helps one become a better writer.