Because of my job, I sometimes get asked about advice on how to improve writing and/or how to get a book published. If you've asked similar questions, here are some books you may find helpful:
The Little Style Guide to Great Christian Writing and Publishing by Leonard G. Goss and Carolyn Goss
The Little Handbook to Perfecting the Art of Christian Writing: Getting Your Foot in the Publisher's Door by Leonard G. Goss and Don M. Aycock
The Elements of Style, Fourth Edition by William Strunk Jr., E. B. White, and Roger Angell
Style: The Basics of Clarity and Grace (2nd Edition) by Joseph M. Williams
On Writing Well, 30th Anniversary Edition: The Classic Guide to Writing Nonfiction (On Writing Well) by William K. Zinsser