The book received a lot a of negative reviews on Goodreads, and these may have been overly harsh. While there were some stylistic issues with the book (Ms. Chestnut has a habit of repeating herself), the information provided was nevertheless valuable.
My only quibble is the wide variety of conditions and behaviors that Ms. Chestnut puts forth as factors leading to potential demonic possession. These include, for example, unkept and messy surroundings.
Don't get me wrong: I'm not defending bad housekeeping; but I have to honestly wonder if we should set the bar that low. She also cites a study indicating that as much as 30% of the population might be affected by negative spiritual influences.
I am reminded of this quote from C.S. Lewis in The Screwtape Letters:
“There are two equal and opposite errors into which our race can fall about the devils. One is to disbelieve in their existence. The other is to believe, and to feel an excessive and unhealthy interest in them.”
The idea being that we then begin to see demonic influences (or other negative spiritual forces) in every corner of life. This is something that we should avoid.
I have to side with Lewis in these matters: Supernatural causation should be invoked sparingly, and only after every other more mundane potential cause has been exhausted. (Let us not forget Occam's Razor.)
This is especially true where the most terrifying form of supernatural causation is involved: demonic influence and/or possession.
That said, I found Ms. Chestnut's book informative, if a bit uneven. There aren't many books available on these matters, and hers is probably among the best.