I'd been meaning to read this for years. I'm not a huge fan of horror, but I found the concept of the Cenobites fascinating. I'd always felt that the movie had some inconsistencies, since it claimed the cenobites offered pleasure and pain, but in the movie, all that was portrayed was pain. I was glad to see that the novella did not have this inconsistency. It addressed the issue as the fact that the cenobites' concept of pleasure was not a mortal human being's idea of pleasure.
I found the characters interesting, fairly complex for a novella. I enjoyed the sense of tragedy with Frank, searching for something and never satisfied, but then condemning himself to more than he ever wanted. The story of Frank and Julia's obsession with him, along with her resentment of her husband, Rory, was all very compelling and tragic. Despite the terrible things Frank and Julia did, I felt for them.
The dynamic with Kirsty was different, and I noticed something that looked incorrect in the book. When my kindle did an X ray, it offered character descriptions and says that Rory is Kirsty's father. This is the case in the movie, but nothing in the novella indicates that. In fact, the way Kirsty thinks about Rory, with his smile making it worth tolerating Julia, these are not thoughts a daughter would have about her father. The novella portrayed her as a friend who had a crush. So it bothers me seeing that mistake in the character description.
The ending wasn't nearly as interesting to me. I can't say quite what I wanted, but it felt to me that the author set up some very interesting background for the story, and then threw it together into a big mess that just made the end result far less interesting than the premise at the beginning. Maybe this is why I don't go for a lot of horror.