The best place to start I’d say is the Thrawn Trilogy by Zahn. First book is Heir to the Empire. Starts out around 5 years after the events of ROTJ. There are a lot of books but that would be the first I’d suggest. Plus there are books in Prequel era, old republic era, during OT era, and post ROTJ.

If you like the starfighter combat, read the X-Wing series. The final book in the series is essentially the writers having a sendoff of their characters before Lucas sold off the IP and killed the EU.

I'd say start with thrawn as well, if you want to start in canonical time the book you want is 'Truce at Bakura'. Also check out the 'Jedi Academy Trilogy' for what I feel would've been an excellent sequel trilogy if you cut out a few of the elements that didn't work and my personal favorites. the tales from Mos Eisley/Jabbas Palace/Bounty hunters/Imperium and Rebbellion, a short story anthology series which give a good ground view of life in the star wars EU.