Reading this when I can is compelling. The new PHB was exciting, but much of it was a process of skipping through the new rules to get to the meat of each class or set of mechanics to get play rolling. Good and utilitarian. The new Monster Manual, however, commands your attention and really makes you want to read it. This is a very good thing. It's not the only book to do this in 2014, either...the 13th Age Bestiary is very much the same sort of tome, one where the reading of the book is sufficient to send your head swimming with neat ideas for future games.
Overall, this book is shaping up to be the best MM since the 2nd edition Monstrous Manual. It's that good.