This is part of the reason I haven't updated. Do you realize how much effort it takes to read this book? But it's so worth it.
Storywise, the book is a compilation of writings by an old man named Zampano, all collected by the narrator after the Zampano's death. The old man was writing a hefty analysis of a documentary about a house that supposedly can change size and shape, amongst many odd things. Through this analysis we see the story of the family that made the documentary, and the sidenotes by the narrator show us his own deterioration due to his obsession with the House (and probably show us what happened to Zampano).
I liked it overall rather well, more than I expected. It rambles in places, and sometimes things went over my head, but I believe that is the point: we are reading a in-depth analysis of a film. Ostensibly this is meant to be fictional nonfiction. It is only the tale of the family, and the narrator's sidenotes, that really bring it down to the reader's level.
Unfortunately it was the narrator's sidenotes that lessened the impact for me. At times his notes seemed to address the story; but more often than not they were neurotic ramblings about his, erm, "activities", which rather took away from the psychological horror aspect of the book, for me, at least. If I read it again I will probably focus more on the "nonfiction" part.
I would definitely recommend the book, but only if one is willing to spend a lot of time. Apart from some things going over the head, it can also be confusing, with text going every which way at certain times, and having to flip back and forth to read relevant footnotes. It's definitely a book you would spend time sitting and thinking through as opposed to a quick read. Still, if you have the time, go for it.
Just don't read it at night. :-)