House of Leaves is actually two stories in one. The first story is called The Navidson Record, which, stylistically, is an academic paper devoting itself to a general analysis of the (fictional, even within the book) much-debated documentary, The Navidson Record. The Navidson Record is about a family, led by photojournalist Will Navidson and his life partner, Karen Green, who moves into a house in Virginia.
Will and Karen hope to re-invigorate their feelings for one another and bring their family closer together by getting a fresh start. Will outfits the house (and the family) with video cameras, in hopes of making a documentary about what a family goes through when making a house into a home.
During a family vacation, the interior of the house undergoes a strange shift in dimensions, and when the family returns, they discover a new closet and a passageway leading from the children's room to Will and Karen's room. The shift goes undetected by the house's cameras. It doesn't take Will long to realize that something is wrong, and, even with professional help from his friend Billy Reston and his estranged twin brother, Tom, Will can't account for the fact that the interior of the house is slightly larger than the exterior.
Eventually, a cold and dark hallway extends out from the interior of their house, though it doesn't exist in the outside world. The hall leads to a constantly shifting labyrinth, where something unknown and dark stalks the maze, occasionally issuing a horrible growl or roar. Will recruits professional explorers to traverse the impossible maze; the rest of The Navidson Record deals with the subsequent explorations into the unknown, and results in several deaths, mental breakdowns, and the asking of many unanswered questions.
The second story is that of Johnny Truant, who inherits the text of The Navidson Record from its dead author. He provides useful commentary on the story, and occasionally digresses into stories about his own life (he covers everything from his his drug and sex addictions to his relationship with his insane mother), and how the horror of The Navidson Record is slowly driving him insane.
This report prepared by Colin Kehm