WONDERBOOK by Jeff VanderMeer is my absolute favorite craft book. I highly recommend it. There’s also a handy companion website (wonderbooknow.com).
So anything by Marion Dane Bauer is bound to be great. WHAT’S YOUR STORY? A YOUNG PERSON’S GUIDE TO WRITING FICTION is a simple, easy-to-read craft book that is a favorite.
If you plan to delve into the dark side, take a gander at Jessica Page Morrell’s BULLIES, BASTARDS & BITCHES: HOW TO WRITE THE BAD GUYS OF FICTION.