Who’s the guy on the right.

The Expanse if the best books series I have read in years and might be the best science fiction series I’ve ever read. The quality does not diminish (in my opinion), and I am glad I didn’t watch the show beyond the first season before reading the books. But there is a lot more than the show covers. I think you can come back to the Novellas later if you like. They are great but you don’t need to read them alongside the main novels unless you are so inclined.