The biggest disservice a person can make when starting this book is, in my opinion, treating it as a straightforward horror novel.
House of Leaves is more like a tapestry, an artwork wherein the technique is what tells the actual story, not the three (or four) adjacent plot points. The book will, more often than not, force you to slow down and intentionally lose you, mimicking Navidson in the labyrinth and Johnny in his head. House of Leaves truly is one of those rare books that manage to transcend the confines of the medium that it takes place in.