The Jedi Academy trilogy is next chronology-wise and has some important story developments, but it's not really all that good. As far as decent Star Wars stories go, in chronological order:

- The X-Wing series by Michael Stackpole and Aaron Allston
- The Thrawn trilogy by Zahn
- The Corellian trilogy by Roger MacBride Allen
- The Hand of Thrawn duology by Zahn (I didn't dig the first book, but the second is pretty good and pretty important in the overall Star Wars extended mythology)
- The New Jedi Order series (has both really good and really bad books mixed throughout, but the good outweighs the bad and it's basically a must-read if you want to keep going into the next generations of the story)

There are some books that are so-so, such as The New Rebellion and The Courtship of Princess Leia. Shadow of the Empire is decent, but is set in the middle of the original trilogy, it's not anything that expands on it like the others.

I haven't read much of the prequel stuff, nor any of the stuff after New Jedi Order.

Others you should avoid at all costs, such as The Truce at Bakura, Darksaber, Planet of Twilight, and The Crystal Star.