Parents asked "how the book recommendation works". Your answer isn't really enlightening: The key here would be how you find similar books that are really recom

Parents asked "how the book recommendation works". Your answer isn't really enlightening: The key here would be how you find similar books that are really recommendable and (especially if you are addressing vivid readers) how you try to minimize recommendation loops and dupes. What database or training did you use to find similar books?