The book Mordecai reads to Ruby, which Carl recognizes from his grandparents' house in Texas.
Mordecai is reading Anne of Green Gables aloud to Ruby in the Saferoom, with the Cleaner Bot listening in. The title gives Carl pause — his grandparents had that book in their home in Texas, and his mom had said it was one of the few things from her own childhood they kept when they moved.
He almost says something about it. Then he sees how tightly Ruby is holding on, understands what the scene actually is, and holds back.
An old novel, read aloud at a saferoom table.
The object that connects Carl's lost Earth to Mordecai's last hours with Ruby.