Why is House by Ted Dekker and Frank Peretti considered a Christian book,only the last chapter has that stuff?

The thing is that I read the book and only the last little bit was really, well christiany. That and the few references to God through out the book, which is kinda expected in a horror book because people get scared and refer to a higher power. But besides those to things nothing else was really Christian to me anyway. What do you think?Why is House by Ted Dekker and Frank Peretti considered a Christian book,only the last chapter has that stuff?
I've read this book and I absolutely love it. When I first picked it up, I didn't know it was an inspiration. It's not really like a christian book, it's an inspiration. I think it's the type of book to speak differently to other people. I, myself, got the message that God is the light and the way and through him, you'll get through it. That kind of thing. But I do understand what you're saying.