I was given the CDs as a gift after having already bought the Air Pilot's Manual books for Air Law/Met and Nav. I used the CDs as my main study material, but did also read those books casually in spare time - it was useful to have them to provide another perspective on some of the more challenging material but probably not absolutely necessary if you have the CDs.
I learnt Flight Performance & Planning from the CDs entirely, and got 100% in that exam, so guess they worked well for that. Also did Human Performance entirely from the CDs, but won't be taking the exam until next weekend...
Also, the confuser is a must-have. It's a great guide to what is expected of you in the exams, and the explanations are useful for the 'other perspective' I mentioned above.