This doesn’t surprise me. Lots of horror has some humorous parts. Stories that are funny with some horror instead often come off a bit odd, like Dean Koontz’s Tick Tock.
Consistent humor is harder for me than consistent horror. I can write funny stuff and many of my characters tend to be sarcastic-funny, but to keep it going for a whole book? I don’t think I could do that. I love to read and write horror, though, so that’s much easier for me.