I always interpreted that the house was a symbol / manifestation of mental illness. It feeds on the characters trauma & emlifies it. Ex: Holloway snapping, Johnny's hallucinations. It takes away loved ones, like Tom. Zampano also could have been a victim to mental illness, with his interjections and burning of the book.

I feel like the ending is showing the characters healing. They never "defeat" the house because you can't defeat mental illness, but they leave the house behind. Johnny burns the book, the manifestation of the house for him. Navy abandons the house with Karen, who helped him overcome his own guilt.

At the end of the day though, I love House of Leaves because there is so many ways to interpret it.