The content seems interesting enough, but I am never sure what to do with books like Japanese Slang: Uncensored. There were some words I recognized, and many others that were new to me. It was fun to read. Personally, though, I don't plan on sprinkling any of these into my daily speech.
My feeling is that this book would appeal to yakuza movie fans, those who want to hang out in the seedier sections of town, and students of Japanese who want to upset their instructors :) A book like this might be worth five stars to anyone falling into these categories!
He puts his terms into narrative form, which is far better than a mere list of words. I was unconvinced by many the folk etymologies, but they made for good reading nonetheless.