This one has the feel of an old-school horror movie, like Psycho, The Exorcist, or an old Hitchcock film - it's definitely a psychological suspense. A lot of it is setting the mood, meeting the characters, and all that stuff. I would say the first two-thirds of the novel moves pretty slowly, although that's not to say it wasn't interesting. Basically, the characters are planning on creating a ghost, with the idea that the mind has the power to do so, and there's a lot of discussion about how this is so. It's based on an actual experiment that took place, and even mentions this fact in the forward and throughout the novel. I enjoyed the philosophical/scientific/paranormal talk that took place - I thought it was all very interesting and thought-provoking, and it made the experiment that much more real to me. In fact, if I could I would read the original book about the real experiment that took place (and I'm not one of those people who whole-heartedly believes in all that stuff).
It's in the last third of the novel that things really pick up. I literally couldn't put the down at this point, and I can honestly say it is one of the few books I've read that gave me goose bumps (and no, that wasn't because the air conditioner was on). I read the end straight through, and finished it at about 1:30 in the morning, at which I had to wake up my husband to tell him I had just read a seriously creepy book (no easy task, that, and all he did was murmur "uh-huh" and roll over to go back to sleep). "Creepy" really is the best word to describe it. I've read scary books, and I've read action books, and this one doesn't really fit into either category. This is one that will haunt you (no pun intended) well after you read it. I find myself randomly thinking about it every once in awhile. The ideas in it are chilling, and the ending is one of the best I've read in a long time.
I would definitely recommend this book, but it isn't for someone who's looking for a fast-moving book from the very start. You have to stick with this one, but in the end it definitely pays off.