Check out
the novels and/or
Star Wars expanded universe...
If you want to read the books, you should follow the main story by reading "Truce at Bakura" followed by "The Courtship of Princess Leia" before starting the THRAWN triology: "Heir to the Empire", "Dark Force Rising" and "The Last Command".
The story where Luke turns to the dark side can be found in the Dark Horse Comics: "Dark Empire" and "Dark Empire II" which takes place between the THRAWN triology and the JEDI ACADEMY triology.
After the JEDY ACADEMY triology you continue with "Children of the Jedi", "Darksaber", "Planet of Twilight" and "The Crystal Star" before another triology, the BLACK FLEET CRISIS, followed by "The New Rebellion" and then the CORELLIAN triology and finish with the HAND OF THRAWN duology.
Then you may start reading all the spin-offs...
(Because then the NEW JEDI ORDER starts and the story takes a turn for the worse...

)
IMO: The first THRAWN triology is the best books, but "The Courtship of Princess Leia" is the best single book...
Edit: George Lucas
recently confirmed two upcoming TV series to continue where episode VI ends, but it appears it's "only" spin-off stories "which will feature minor characters from the films"...