Hi there,
My suggestion - skip the Butt book. Although, it has information on exercises to lift your bum, and a section on nutrition with recipes, if you're a seasoned exerciser (and I know you are!) you won't find anything new in this book. In my opinion, it's good for beginners, intermediates. The exercises outlined are the classic, tried and proven lower body exercises (you're already doing these with Cathy). If you're still curious, visit a Barnes and Nobles or Border's book store and see if they have it in stock. I found one at Borders and spent an afternoon in the store reading it and decided not to buy it.
The Glutes issue of Oxygen, however, is worth the money. It's a compilation of past issues of Oxygen that focused on lowerbody training. Lot's of variety. It's a keeper. I have it for over a year and still refer to it.
Alexandra