Hi,
I know aircraft performance very well, and if your prepared to trust me, the best performance book on the market today, in an easy style read with good pictures is the one from Atlantic Flight Training. It has a picture of a Cheetah (animal) on the front. It was written by Jacqui Suren who I can also say is a very good lecturer, a goddess dare I say. This book deals with what you need to know for the exams, i dare you not to understand what is written.
However, I hear that there might be some competition for this book
Pugs