I’ve never really found that his books promote Catholicism in any way, but I have noticed that any negative portrayals of Christians are usually of Fundamentalists, etc (Mrs White in Carrie, anyone?), though those negative protrayals usually don’t sit well with me. Catholics, on the other hand, are usually portrayed in a much friendlier light.
For instance, though Fr Callahan seemed to lose his faith at the end, Salems’ Lot had a clear message: you need Jesus to defeat evil. Perhaps I am mis-interpreting it, but the scene in which Barlow tells Callahan to put down the crucifix actually had huge meaning to me. Without faith in the Passion of Christ and His love and mercy for us, the symbol of the crucifix will not help us. You do not defeat a vampire with a crucifix because of superstition or magic, you defeat a vampire with a crucifix because you are asking our Lord to come between you and the evil you are facing!
A positive portrayal of Christianity was probably most apparent in The Girl Who Loved Tom Gordon. Trisha spends the whole book contemplating whether God is just a vague force of the universe or the loving, personal God that we believe in. In the end, she agrees with us because she believes that she could not have survived in the woods without Him. I really, really liked that.
In general, I would not recommend King’s books to just anybody. I think it takes a certain kind of person to not be completely turned off by his brand of horror.
On the topic of Pet Sematary, I am just starting the book. I have seen the movie and have heard that it is probably his most disturbing work. Could somebody go into a little more detail for me, since I already know the story. I’m a little unsure I want to finish it now.