Helpful indeed. I didn't know there was already a resource/book on the market.
Just had a quick glance. Based on the ToC I think all topics are covered. But I'm a bit wondered about the number of pages this book has: only 650 pages. The K&B6 book has more than 800 pages. And for the OCPJP7 the number of topics are increased. That's why I expect the study guides for the OCPJP7 certification to have more than 1000 pages. That makes me doubt a little bit about the book being too comprehensive to have a good and clear understanding. For example, the chapter on generics and collection is 60 pages, in the K&B6 book it's 120 pages (95 pages if you ignore the self-test with the correct answers).