>how do you find books they'd be interested in? Like, that's the goal! You can't just assume the solution.
What a strange question?
If they are interested in fantasy movies give them a fantasy book. If they're interested in mystery, the same. If they're interested in Dinosaurs, the same. How is this some great challenge? The things you like to read about are the same things you already like... Are you implying you know nothing about your daughter?