As a non-fiction book we'll just say I'm a bit skeptical.
As a fiction book it was awesomely bad. I mean that with all respect. The writing could have used a lot of polishing up. To be fair I was reading an ebook version, so that could be mostly why there were lots of typos/wrong words used.
Some of these typos/wrong words verged on awkward and took me out of the story.
It was such a pulpy book. I've read a few demon possessed houses and demon possessed people books before. Some were amazeballs. Like grade A horror right there, this one was good only because it was like reading a pulp fiction paperback. I've also read A LOT worse.
I still say I preferred the movie, but I've only seen the first one.