Not a book report. A book journal. The difference is that no one grades it, it's not for school, and your kid can use it however they want.

Some kids draw their favorite scene. Some rate books on a scale of 1-5 tacos. Some write one sentence about how the book made them feel. Some just list the title and a thumbs up or thumbs down. The format doesn't matter. What matters is the habit of reflecting on what you've read — which is the metacognitive skill that separates kids who read from kids who devour.

A blank notebook works. A dedicated reading journal with prompts works. A note on a phone works. The medium is irrelevant. The practice of stopping after a book and asking "what did I think about that?" is what builds a reader who knows their own taste.