The Exorcist - William Peter Blatty

I've had a hardback dust-jacketed copy of Blatty's book for a while, and finally got a chance to read it.  A little hard to read in the beginning - the author strings together a lot of adjectives and it's a bit opaque, but it gets better as it goes along.  Not all that scary by current standards, and the main impression I got was how hard it is to actually conclude that a case is one of demonic possession, thus justifying an actual exorcism.  Assuming the book has the standards right.