Here is a list of reference books I have in my library. 
These books help me in the process of being a 3D animator.

The Animator’s Survival Kit by Richard Williams This book is awesome.  I recommend this to every animator to have.  I learn how to animate different variations of walk and run cycles, quadruped walk cycles, and many other ways to show weight and movement.  Even though the examples in the book show 2D animations, it is still useful for 3D as well.  To me, it is the bible for all animation.

Animals In Motion by Eadweard Muybridge Animating a quadruped or any other mammal is hard.  You have to concentrate on the legs, shifting of the body, timing of the footsteps, etc.  There is a quadruped walk cycle format in The Animator’s Survival Kit but it wasn’t enough reference.  This will help you to see different animals… well, you know… in motion.

How to Draw Animals by Jack Hamm This is another book that will help in studying  quadruped movements and understanding the anatomy of each animal such as canines, horses, and large mammals.  All the quadruped walks cycle are drawn out versus Muybridge’s Animals In Motion, which is all photographed.  You may have a hard time knowing the timing each foot step in a photograph if the animal foot doesn’t land in a particular frame or timing.

The Actor in You by Robert Benedette Every animator should have an acting background or at least understand the concept of acting.  Often animators act a scene because it is a good way to flesh out your 3D or 2D character.  This book teaches you breathing techniques and how to utiliz your body to tell a story

The Ballet Book by Nancy Ellison Lots of dynamics poses, such as dance, will help you to bring out your character’s personality.  Also this book has quotes and stories that may be inspirational for us animators, or a good dieting and exercise book.

The Ultimate Book of Martial Arts by Fay Goodman A great reference to see different variations of martial arts and philosophy.  Not only is it great for animators to gain insight in fighting poses, this book is also good for concept design because the different uniform and weapons reference for each art.

AfterEffects in Production by Trish & Chris Meyer To push your animating skills a bit more and show an interesting scene, learning Adobe AfterEffects will be a good skill to have.  There are some awesome tutorials such as 3D layering.

Film Art: An Introduction by David Bordwell & Kristin Thompson A great reference to find inspiration in cinema.

The Technique of Film and Video Editing by Ken Dancyger Okay, working on a 30 second animation is a though job, but how would you know when to cut it?  Knowing when to cut a scene or applying sound will push your animation to another level.  Dancyger will give you editing theories in his book.

From Word to Image by Marcie Begleiter Cinematography and storyboarding is pretty much a requirement in animation.  As an animator, we should know how to tell a story by movement and scene shots.  In the 3D world we can push the limits of cinematography farther than filming a scene in the real world.

How to Draw Comics the Marvel Way by Stan Lee & John Buscema A great book to learn how to bring out a character personality by dynamic poses, showing a good shot in a scene, and presenting an excellent storyboard.

How to get a Job in Animation by Ed Harris If you are looking for a job, this book will help.  Ed Harris guide you through the tips and tricks of getting an animation job from forming you resume and reel to getting recognized at SIGGRAPH.