Read this textbook cover-to-cover and then go through ACSM's Certification Review, and you should be fine on the CPT exam. This text can get pretty technical, but you don't need to memorize everything to do well on the exam.
I do not recommend this text for use as a reference guide if you work in a regular gym. The ACSM CPT exam is very clinical in nature and the information is geared towards use in a physical therapy/rehabilitation setting. For instance, even though the text highlights how use of free-weights is better than use of resistance machines, most of the exercises covered in the book are performed on resistance machines. I also know very few personal trainers who own a stethoscope and a BP cuff or who make regular use of VO2R calculations when making exercise prescriptions.