This is the Bible for people who are trying to understand animation. I write books for a piece of 3D animation software, and everyone I've talked to who is into animation and has read it agrees with me: this book is invaluable. There is too much knowledge here to assimilate in one or even two readings. I will be using this book for years to come as a reference, an inspiration and as a way to "return to principles" when I lose my way.
