It's just that early on in the book a house acquires an extra room while the occupiers are away for the weekend. Subsequently it turns out that the house is about an inch and a half longer and wider inside than out. Later, a doorway appears on the inside of an outside wall with a long corridor leading away into the distance.

After that things get a bit odd, so if corridors start appearing move out. Or at least don't investigate.

Ooh, that does sound good.

That's one part of the book. It's encapsulated in another layer about a study (partly-finished, by a dead Mexican man) of a nonexistent documentary covering the events. In turn, that's within an account of events in the life of a psychologically troubled Californian trying to piece the other two layers together. There's also a strange thread I don't understand about the latter's relationship with his dead mother, copious and multiply-nested footnotes covering all of the above, written in different fonts to indicate the varied authorship, some scored out, including a load of stuff about a minotaur. It's obviously a haunted-house story, but there's a house and no ghost.

If this makes it sound like a strange and infuriating book, that's because it is. It's also an absolute doorstop. Enter at own risk.