As a work of literature it's not really the best writing. Certain characters are a bit one dimensional or just annoying and the plot is not the best. As a big fan of the show though, I did enjoy bits of it. There is some interesting back story but the two cases aren't the best. One case involves recreations of murders from Edgar Allen Poe's stories and the other is a haunting at a friend of Ash's house.
Overall, it was just okay, but I would not recommend it if you did not like the show a lot. If you really want a good story line from the Supernatural universe go find some fanfiction.
I was not a big fan of this book, I love the show and so some parts of the book was cool. In gerneral the writer seemed to completely disliked Dean and made him seem dumb, and the writer seemed to be in love with Sam.
The plot was ok, but just ok, I wouldn't recommend buying the book, but getting it from paperbackswap wouldn't be bad if you wanted to read it.