Thank you for posting it! I will have to buy the book by St Clair. Thanks goalienan, I was wondering and then read your post. Amazon it is. This sounds a lot like what went on in "The Exorcist". I thought William Blatty based his book on the exorcism of a young boy.
Like Coldethyl said, the compulsions to do completely irrational things also remind me of OCD, and people suffering from those type of thoughts should not think that they are possessed. Just thought I'd throw that in there, in case someone reading here was having those types of thoughts.
I have to agree with both you and Coldethyl on OCD..my granddaughter has it and until we had it diagnosed it was very frightening.