Rach's Reading Club

Good question! I had to ponder that because I've read them in order of release. I guess they could work in chronological order, but because of the order in which they were written, they do contain spoilers because it's assumed you already know what is to come.
So, I think order of release is probably the best way to go. The original trilogy is definitely worth a read. The Ballad of Songbirds and Snakes is a good read as well.