I have one reason you should get this book.
The entire book looks like a comp. All illustrations are rough sketches of the ads that they are talking about.
Because the point of the book is concept now, design later. You should make roughs and tissue paper and sketches and whatever you may call it, as many as you can, as simple as you can to explain your idea. When you have it, the idea that scrawny little sketch jumps out at you and the designing can begin.
Put that mouse down, leave the wacom tablet alone. Take your time to look through this solid, informative and fun read. Giggle at each comp that you instantly recognize the ad in. Learn the lesson: have the concept before the computer.
Honestly, every client out there should have this book.