I don't remember if I reviewed the book House Of Leaves when I finished it, so here we go.
At its base, a Lovecraft style horror. It is to my knowledge absolutely unique in the genre. There are layers of the story designed in such a way that the reader is in the world of the horror and potentially victim to the monster.
Also unique in my reading experience is the way that the book absolutely ignored every convention of book layout for effect. Font, color, and layout are all abused. Repeatedly I found myself flipping back to see how far back a trick had been played on me. More than once when I realized how the book was sucking me into the story I swore out loud.
I do not exaggerate at all when I say you need a real physical copy of this book if you plan to read it. An ebook or audiobook absolutely will not do the job. You couldn't convert it without destroying the artistic merit, think braille playboy.
I finished it months ago and I still think about it regularly. I have added other books by Mark Z. Danielewski to my to read.