Just about every writer of worth, and some of none, have written books on writing. I don't know how many are on my shelf. Every time I go to a writer's conference, I add new ones of the writers I've met at the conferences, especially if they are good workshop leaders or talented teachers. That's what I thought of Nancy Kress when I met her at a conference. She was personable and a good teacher.
As for books on writing, my favorites are two books by Natalie Goldberg, Writing Down the Bones and especially Wild Mind. I have bought and given these books away numerous times. I remember having a writer's breakthrough back around 1990 with the help of these books. A couple of weeks ago, I ran across Writing Down the Bones at a conference and snapped it up again. Going through it is like spending time with an old friend who really cares about my writing. I'm using it to help me keep the conference glow going.
Another book on writing I appreciate is On Writing by Stephen King. King is so good at voice, he even has a great one for himself in this book which is part text on how to be a good writer and part memoir. His mix of self-disclosure and tips on writing could not be pulled off by anyone else. The best way to read this book is in audio format, because King reads it himself. His casual tone feels like he's just taken a seat in my livingroom wingback chair and started talking while I pour the tea.
I owe a debt of gratitude to all of the writers who have contributed books on the topic of writing. They keep me going when I lose momentum.