Wow. Where to start? 
 Very little can clearly and definitively be stated about Mark Danielewki's book; it is dense and confusing, it is playful and frustrating. It is a work of either genius or a huge illusion of smoke and mirrors. I certainly lean toward the former. 
 The story of the main text is that of a supposedly famous film by Will Navidson, a celebrated photojournalist, settling down from his travels on assignment around with world with his partner and children in a house in Virginia, only for a strange hallway to open up in the house that seems to defy both the dimensions of the building and the laws of geometry. It is this central plot that leads the novel (some would even argue with that noun although, while he plays with the form and stretches it, a novel it certainly is) to be filed under 'horror'. 
 This text, however, is being presented as an unfinished manuscript by a blind author Zampano, discovered and edited by one Johnny Truant, an Angelino apprenticed at a tattoo parlour in the city. Johnny's footnotes become longer and more invasive, appearing often to have little to do with the text and frequently running on for pages at a time - on top of footnotes by the mysterious Zampano, so Johnny's footnotes are often secondary, and become increasingly nested, to the point of absurdity, in some cases leading to appendices which are footnoted "missing". 
 This textual confusion is furthered by the inclusion of many quotes from cultural arbiters and experts - interviews with Stephen King and Stanley Kubrick, criticism from Jacques Derrida and Camille Paglia and Hunter S. Thompson - and many others more obscure and, indeed, entirely fictional. Actually, while this film is written about as being a defining cultural moment, Johnny himself has never heard of it. The text and Johnny's footnotes are presented in presented in different fonts and, as the impossible labyrinth within the house is explored Danielewski introduces increasingly bizarre text layouts - text directionality changing on the page, being printed upside down, notes embedded in the middle of the main text, words being as important for their pattern on the page as their meaning. 
 So, what is the book about? It could be read as the story of the impossible house, although the reader would have to ignore a massive amount of the book (there is actually a wonderful radio adaptation which does an admirable job of dramatising this aspect), the hallway and labyrinth to which it leads can be read as a metaphor for the problems in the relationship between Navidson and Karen - but Johnny's story is even more interesting and obscure. One of the appendices is The Whalestoe Letters, correspondence from Johnny's institutionalised mother, which makes (some) sense of some of his own background. Do the rest of the appendices add to the tale? The odd poetry and notes and quotes and sketches? I don't know, but it all feels like it belongs. Is everything David Lynch includes in a script meaningful, or is he sometimes just fucking with us? Even if he is, if it still adds to the stor, it still belongs. 
 Some of Danielewski's influences are clear - I see Borges and Calvino and Alasdair Gray, and I know there are many, many I miss - but the book is so beautifully constructed, so much its own thing (and so knowingly self-referential) that reference spotting never spoils the ride. I have no doubt that this is a work of utter genius to which i will return, if only to see what I've missed on a first reading.