Not the most timely book review, but then I didn't watch the movie until last fall. Finally strapped some steel to my backbone and was disappointed to find the movie more creepy/disturbing than actually scary. Some parts were gross (the vomit), but more often than not it was sexually disturbing.
The book was not so different. It wasn't so much scary as weird. It explained a little more than the movie did, as is often the case with books. The beginning in Iraq wasn't such a non-sequitur and Merrin's previous experience with the demon was touched upon, which I don't remember in the movie. However, there were a lot of questions that were NOT answered by the book, and I truly hate loose ends like that. Some were minor, like the fact that Karras died before he could deliver Kinderman's message to Engstrom about Elvira. Now I'm wondering if Engstrom ever found out that his daughter was getting help, and how his wife dealt with the news. The more important questions dealt with the demon itself: what demon was it? The book alludes to a mesopotamian wind demon named Pazuzu, but also makes reference to Legion, the demon driven into the pigs in the New Testament. It is also never explained how or why the demon chose/met/became aware of Regan, whom it posseses. The biggest question that is the most aggravating to me is that when Karras originally interviews the demon, he asks it if it would die if Regan (the host) died and the demon replies that it would not. However, when the demon posseses Karras and he throws himself out the window, the demon disappears from the story, supposedly having suffered the demise Karras inflicted upon himself and his possessor.
Despite the questions that were left unanswered the story of the book was interesting. Though I thought the writing was quite choppy and confusing. I found the first 50 pages or so extremely tedious to get through. Not only was nothing happening in the story, but the writing itself made the story hard to follow. The mother's character, Chris MacNail, seemed to be especially hard to follow at the beginning. Here's an example of her thoughts as written by Blatty: "Hi, little wonderful girl next door! Can I speak to your husband? Your lover? Your pimp? Oh, your pimp's in the poorhouse? Avon calling! She stuck out her tongue at herself. Then sagged. Ah, Christ, what a life! She picked up her wig box, slouched downstairs and walked out to the piquant tree-lined street." (Page 17-18) Her entire reverie made no sense whatsoever, and had nothing to do with what was going on in the story: she was getting ready to leave for filming and made a silly face in the mirror.
Either way, by the time I realized what it was about the writing (I always believe in giving books anywhere from 50-100 pages to capture my interest), I was too invested in the story to not find out how it ended in the book. It was a pretty good story, but with the confusing writing and the unanswered questions, I'd say that if you want to know the story, watch the movie. Don't waste more time than necessary for a book with loose ends and confusing writing, no matter how good the story.