Celtictarot and RiverRunsDeep, when you get a chance will you talk a bit about the guidebook? I've had the deck for several years (love it) and always shied away from the guidebook because i assumed i wasn't really interested in the book of Enoch. It's kind of a weird question but if you're able to talk about Belanger's tone or voice she uses? I mean is it down-to-earth language; yeah, i know, they're angels... And i could be fine w/ woo-woo language, paranormal whatever. By this point, i've read several things about John Dee and Enochian from that angle that i might be fine w/ anything Enochian. But i read fine w/ the deck w/out any book, and if memory serves i wasn't bowled over by the lwb, but we all know how different a companion book can be to that.
Get the book.
Admittedly, I haven't read it in depth yet, but I like what I'm seeing so far. It provides a lot of worthwhile and well researched information without being overwhelming. I do find Belanger's "tone" to be down to earth. Her presentation of the material is serious and well thought out. Nothing very woo-woo here, but also nothing so scholarly that it makes for dry, pedantic reading.
The book has three main sections. The first section details how the deck was created, the inspiration, influences, artistic process, etc. The second section presents the mythology behind the Watcher Angels. There are about 10 pages that discuss in detail the Book of Enoch and how it correlates to the deck. But while Belanger says the scholarship behind the Book of Enoch is important, the focus of the deck is "less on the facts surrounding the work and more on the story". The third section, and the "meat" of this book, is dedicated to the descriptions and interpretations of the individual cards. Each card gets roughly two pages to itself.
I would agree that this book isn't necessary in order to read with the cards, but I think it makes a wonderful addition to the deck. If Watcher Angels is a favorite of yours, I don't think you will regret getting the book, IMO. No regrets here!
Mostly just my initial impressions, but I hope they have been helpful.