Zacker's book is much more compact, and gives you the quick and dirty. He hits the topics hard and fast. If you need to work through the material in the least amount of time, this is the book for you. Holme's and Thomas's book goes into much greater depth and specific exam preparation. Zacker presents his material in a clear and methodical manner. His writing style is fluid and easily accessible. He has a knack for presenting complicated material in a way that helps clear it up quickly.
