Particularly ones set before/during/shortly after the prequel trilogy? I have a pretty good idea of where to go for the New Republic stuff.
I don’t read much in that timeframe but…
- The recently released Kenobi, set immediately post-ROTS was excellent.
- I read Rogue Planet years ago and remember liking it well enough though I don’t recall much else. It’s set a few years post-TPM, early in Anakin’s apprenticeship.
- I’ve never read Shatterpoint because it’s a Mace Windu book and I don’t care for him, but most people who have say it’s excellent.
- If you haven’t read the novelizations of the prequel trilogy, particularly the Revenge of the Sith novelization, drop everything and do that.
- The only other things I think I’ve read in this time period are the YA Jedi Apprentice (which follows Obi-Wan early in his apprenticeship to Qui-Gon) and Last of the Jedi (which follows survivors of Order 66) but idk if you want to read YA.
Immediate? Kenobi. Very good.
To understand the Sith and their thinking – Darth Plagueis
Best before A New Hope – Karen Traviss Commando Series
Comics about Moff Trachta.
Imperial era – reference books on Guide to Star Wars Characters
There are more on Wookieepedia