My number one reading tip for writers is that you should read widely. That said, there are useful books specifically about writing.

• 100 Ways to Improve Your Writing by Gary Provost. A collection of short tips for writers. I recommend getting a physical copy so you can browse it when you’re looking for ideas for improving your writing.
• The 7 Secrets of the Prolific by Hillary Rettig. On being productive writer and on writing as a career. Some of the best writing on perfectionism and prodcutivity that I’ve seen. See jml’s notes for a summary.