This book is a description of the Project Management Institute's standards. It is an interesting albeit long read with a lot of information packed into its roughly 400 pages. I had to read it 3 times in order to better understand the PMI's methodology.
If you have some project management experience, and want to take the PMP certification test, you will have to read this book. However, I would recommend that you supplement your reading with books focused on preparation for the PMP exams/tests.
If you are an expert or experienced project manager, I recommend THE BLACK BOOK OF OUTSOURCING (Wiley Publishers) by Dr Doug Brown & Dr Scott Wilson, as the Outsourcing Industry is begging for seasoned Project Managers in all phases and career steps. This book will tell you where to find the jobs and how to qualify. Excellent way to capitalize on the phenomenon personally.