I never read the prequel. I would start with the first book which is a fine intro to the series. I expect the prequel might work better when you have read at least some of the books.I’ve been meaning to read the series. Where do I start? The first book or the prequel or somewhere else entirely lol
I'll also note that the first book starts off very derivative/evocative of Tolkien. That diminishes somewhat even within the first book and definitely as the series progresses. It is very original and its own thing, even if it is based on the trope of an evil lord who was defeated in a prior age returning and being opposed in accordance with various prophecies.