May be off target a little but I read a book way back in the 80's that scared the yell out of me. Malachi Martin was a Catholic Priest who was sometime interviewed on Art Bell back in the day. Anyway, he was also an exorcist. He wrote a non-fiction book called "Hostage to the Devil." It was about exorcism. Now, I'm not saying it proved the existence of the demonic to me. But, as a spritual or as a Psycological read it really was errr, disturbing. Don't know if it's still in print but if it is I would recommend it if your curious from either a spiritual or just cultural angle.
I am going to say yes I believe in ghost because I have been in enough situations where I really feel that I saw or felt something that I would say was a spirit / ghost. The best was at a hotel in Seattle. We stayed at the Moore Hottel next to the Moore Theatre, I say if you want to see s ghost stay there are you will see something.