So I didn't actually read this book. What I did do was spend five minutes looking at it in the bookstore yesterday. It's a pretty terrible basis for a review, but that's what I'm doing.
The book in question is
"The Supernatural Book of Monsters, Spirits, Demons and Ghouls" by Alex Irvine, a reference book for the show "Supernatural".
There are two glaring problems with this book, and the introduction showcases both of them. It reads something like (not an actual quote, based on memory) "Hi, we're Sam and Dean Winchester, and we've been hunting things our whole lives, ever since some thing killed our mother when Sam was six months old and Dean was five." Okay, wait a minute. First of all, Dean was four when their mom died. Any real fan of the show knows this. And first person plural? What kind of a weird-ass way is that to write a book? And a reference book, at that?
A little bit more skimming shows that this is continued through the book -- "we" did this, "Sam" did that, "Dean" did something else.
Nope, no index. Entries separated by monster. References to events in at least "In My Time of Dying," don't know if it goes beyond that. A big list of, um, European demons in the back. Not related to the show. Okay.
The entry on Reapers references
both the episodes with Reapers -- "Faith" and "In My Time of Dying", with mentions of "and Dean discovered they could shapeshift when he spent some time with one" which Dean doesn't even remember so, again, minus points for inaccuracy.
And that's as far as I got. Why don't they ever have fans write these things? If it were accurate, it might be worthwhile. Don't bother sacrificing a tree for this one.