i first read the book in my teens, before i had even seen the movie and i knew it was a fantastic story but i never appreciated how well it was written and put together. it is in fact the same story as the uncut directors version of the film which has a large chuck re edited into the movie that makes it even more detailed. the chunk that is missing is the bits where regan is taken to various medical specialists and the science is followed rational physiology and psychological concepts explored. the actual exorcism happens right at the conclusion of the story and all the way through can be countered with a scientific balance. 

the book is amazing, it really is very good and if you think it's just a horror novel your mistaken, it's about so much more. loss of faith, science vs religion, love and death. even the detective whom features as a sort of minor character is left seemingly lonely and alone and wondering about what he was investigating. 

i wasn't scared reading the book, intrigued at the way wpb had written such a tight philosophical yet page turning novel.