Definitely House of Leaves. A story inside of a story, inside of a story, with all narrators being just a bit crazy. Text of different fonts, going all over the place and even upside down based on the story. Just make sure to get the physical copy.
Oh I didn't know about this. You're talking about The Familiar, right? I don't know if I'm up for another 5 books like this but now I really want to try.