Has anyone used this book, and can comment on whether it is any good? I have used the 520 Ans... book, which was great but impossible to get now, and the Inte'graal guide, which seems have quite a lot of mistakes, poor directions and inconsistencies (and doesn't have oblig grades). Both were borrowed and I'd like to get a guide of my own, asking on here since I find it hard to tell whether a book is going to be any good without actually using it