Parts of this book are incredible, parts rambling nonsense. In the first half of the book there is 1 page of story for every 5 pages of commentary on God, Evolution, Pain Therapy, "Modern Science", Metaphysics, Causality, Etc. all from the perspective of good old 1983.
It's written strongly and laced with undertones of an exhausted father who's children just refuse to see the light, despite all of the "facts" to the contrary. Many times the book makes a point of how "facts" confuse the truth which seems to be almost blatantly retarded to your average modern atheist with 27 years of additional scientific evidence for everything posited as one of these truth confusing "facts".
The storyline is entertaining but obvious. The book is well written and the transitions from the rabbit trails (which seem to be the reason for this book) to the main storyline are cohesive and often times so rapid it's startlingly subtle. You suddenly realize you're reading something you care about.
This seems to be more of a very loose tie in than a direct sequel to the Exorcist. The writing style is a vast departure, the detail paid to the story is much more minimal, nearly back-burner to the platform for expounding his theories on the universe. Even IF this book had picked up the day after The Exorcist and continued the exact same story, just due to the way it's written, it wouldn't feel the same. Let me go all William Peter Blatty and explain: What if Peter Jackson had directed Fellowship of the Ring, The Two Towers, then suddenly died of an embolism and Return of the King was done under the exclusive creative control of Michael Bay. Wouldn't be the same.
I do not want to be wholly negative about this piece, it's just disappointing if you're expecting what's promised on the cover. This man clearly has a talent for writing and using minimal words to convey vivid imagery. Do not expect to be scared by this book, or if it starts to get uncomfortable, at least know it's very likely the next five pages will be so senselessly unrelated to the story that any suspense you were feeling will be replaced by a quiet sigh and the question of when you can return to the book you thought you had purchased.