I just reread Graham Walmsley's Play Unsafe. It's helping soothe my fractured Mojo.
I recommend it, but if you figure the worth of a book by its page size and count, you will be disappointed. As noted by the first reviewer on DrivethruRPG- the pages are digest-sized and there's only about 80 of them, and the product is $8.00.
If however, you choose to judge a book's worth based on its content then it might be for you.
Are you GMing, but find yourself dreading the next game?
Are you fighting to keep your players on your storyline?
Do you love reading books about game mastery because your as weird as I am?
Then this book is worth your time.