What is an example of metaphor in the book, All Our Wrong Todays: A Novel?

While only a "setting" in a metaphorical sense, the collective minds of these versions of the same character are treated like a physical setting. Mastai describes each one of their minds as a room; each of which are nested inside each other. The walls of these rooms are made up of the memories of each specific character. When the three of them fight for control, they fall through odd, twisted versions of each other's memories.