The Exorcist, William Peter Blatty
Despite the title this book is more about the demonic possession of a twelve year old girl than it is about the exorcist. The book starts with a prologue introducing the reader to the exorcist of the title but does not inform the reader that this is the exorcist.
The appearance of the exorcist is presented in the last 50 pages of the book.
This is the fortieth anniversary of the publishing of The Exorcist. I believe that that which is described in the book would, at the time, be terrifying but because this book so very heavily influenced the horr