House of Leaves is an experience. I've decided not to go into the plot, because it, (they?) really can't be fully explained in such a limited venue as a book review. Depending on how you look at it, there could actually be 5 different plots going on, perhaps more, and again: limited venue.
After mulling it over for a few days, I find that I'm comfortable saying the following:
1. The portions of the story dealing with the house itself were my favorites. I think these sections were truly scary-among the scariest I've ever read. I've seen other reviewers say they weren't that scary and I've been thinking about why that is. All I can come up with is I guess it depends on what scares you most. If it's a guy with an ax or a ski mask, or maybe Hannibal Lecter, then perhaps this wouldn't be that scary to you. However, if you're afraid of the big, black, empty and what might be hiding in it, then you will most likely be scared and/or disturbed by this book.
2. If you're looking for an immediate pay off as far as scares, this book is the wrong place to look. The building atmosphere, the use (sometimes excessive?) of foreshadowing, plot lines suddenly left hanging while other lines are pursued are just some of the techniques used to keep the reader off balance. This is like the long term con, not 3 Card Monty.
3. If you think you're going to come out of a first reading knowing everything there is to know about House of Leaves, I just want to tell you- you're not. There is SO much going on here, it's crazy. Mythology, song lyrics, poems, quotes, codes and themes all combine to create this unique story. I'm not sure it's even possible to "get" everything you're supposed to "get" on a single reading. Maybe it is and I'm just dumb? It's definitely possible. ;)
I don't know what else to say, so I'll wrap it up. I recommend this book highly, solely for the experience of reading it. The varied plot lines may or may not appeal to you as I've mentioned, but the experience of reading this book itself is not to be missed. What books have you read that could be called an experience? If the answer is none, you need to read this book!