Loyalty is a great thing, but even Mike will tell you that their book is not an end-all on the subject of bp revolvers. His attempt to update it and improve the pictures last year was thwarted by his publisher; I'm sure he would love to be able to finish that effort. In the mean time we'll have to resort to acquiring other books - creating a library, as it were.
Don't get me wrong - I think it's the best one on the subject, that's why I recommended it, and if you can only own one, that's the one. But it doesn't have everything, so you do need a couple of others - thus, no single best book.