I’ve had good luck finding interesting ebooks using Hoopla. If you’re unfamiliar with it, it’s tied to your public library and lets you check out ebooks (and movies, but haven’t used it for that). It’s a good way to read a book to see if it’s worth buying. Unfortunately, I’ve read that many libraries are moving away from it because of its pricing model.
Overdrive/Libby is a similar service, but the selection is very limited, and popular books typically have long waiting lists.