Or if not my books, then other people’s books. Books of people you like, or want to be nice to, or whatever. They are begging for your reviews. They dream of your reviews. If their books get enough reviews, the algorithm notices!
In fact: I have just gone through my purchases and reviewed some of the books that I have bought and read. If I can do it, then so can you. I challenge you to do it, in fact.
…But start with mine.