Literary Fails: Totally (sic)!: 101 Crazy Query Letters Sent By Writers in Their Quest for Publishing Fame by Sharlene Martin, Anthony Flacco and Ray Toler
This is a hilarious book for anyone writing/sending/getting rejections for query letters. When you find yourself worried and stressed about queries, this will put a smile on your face, and it'll make you feel much better about your own letter (hopefully)!
Writing and Selling Your Novel by Jack M. Bickham
A good book about creating a cohesive, coherent story by correctly placing and pacing scenes.
On Writing by Stephen King
Terrific glimpse into the life and craft of one of the most famous writers of our time.
Writing the Breakout Novel by Donald Maass
This book is in just about every "Must Read" list for writers, and it should be. It's a great introduction into the world of serious writing.
The Writer's Digest Character Naming Sourcebook by Sherrilyn Kenyon
The perfect resource for all your character naming needs. Names are sorted by country of origin, and name meanings are included. The book also includes a "Most Popular Baby Names" list by year.
Psychology for Screenwriters by William Indick, Ph.D.
Let's just call this one "Psychology for Writers". With movie examples of various psychological archetypes, this book helps writers understand the inner workings of their characters.
Save the Cat! by Blake Snyder
Yes, it's another screenwriting book, but it explains character building, story pacing and story pitfalls in a way that's useful (and fun) for novel writers, too.