They're really good, but while I may be influenced by having seen the show first, I think it's one of the best adaptations I've ever seen, especially given the offscreen drama with budget, network, cancellation, and some unfortunate awfulness from one of the cast members.

Some characters are slightly better in the show, some in the books, but I've rarely seen a show nail the tone and spirit of the source material like The Expanse did, but that said, there's so much more space to live in the characters' heads and soak up their world in a book, that's it's absolutely worth it to go back and pick them up, and they're easy to start and stop, I'd say.