Although the AFE book had some use, I found it had so many errors, that it was just very frustrating to use. Coupled with the fact that the "explanations" it provided were usually references to books that you probably didn't have (or incorrect references to books that you did), I regularly gave up using it whilst revising.
The confuser is a pretty good book for revision - it's usually accurate, and has reasonable explanations in the back.
People have this funny idea that using these books is in some way cheating, but it's no different than using a past paper for your school/university exams.
A thorough understanding of the subject is obviously the key, but it doesn't necessarily fully prepare you for answering exam questions. It's important to understand, though, that being an expert in answering exam questions doesn't neccesarily demonstrate a thorough understanding of the subject.
(but now I'm starting to witter on ....)