There are a lot of PMP Exam prep books available on the market and the most efficient way to compare them is through Amazon as you can browse through some pages at the convenience of your computer:
During my PMP Exam preparation, I purchased the The PMP Exam: How to Pass on Your First Try, Fifth Edition by Andy Crowe which is specially written to help you pass the exam and “only the exam”. This PMP book is unlike other books on the market which contains tons of project management knowledge, this book contains only the necessary knowledge for the PMP exam. Most importantly, it is an easy read. I finished reading it in a morning. Plus, it includes a PMP mock exam which is quite similar to the difficulty and format of the real PMP Exam.