(He'll let her get comfortable first before he picks up his book again and sets it down in front of the two of them, wrapping his arms around her to do it. He shows her the cover-- it's an airplane in the sky,)

It's about flying.

(Which sounds silly when he says it to her. He can't help but laugh just a little sheepishly now that he realizes this,)

These days, people are traveling and sending goods by air. (Of course he knows this and as a Rider, he even understands it to a certain extent. But he's always been interested in ships and moving around, whether it be by sea like in his days or air like these days.) People have come a long way since steam ships.

(Of course, that's human nature. When freed from limitations like class and an oppressive system, they can accomplish anything.)