Honestly, just pick up any other book and give it a go, if that doesn’t work drop it and pick up another one. Nothing depresses me more than those people - adults - who finish reading the last Harry Potter book and then pick up the first one and start over again. I’ve heard nothing but good things about Rick Riordan as far as getting kids into reading, that all happened a little after my time though (and I was already big into reading as a kid)