The Jedi Academy Trilogy

The Jedi Academy Trilogy by Kevin J. Anderson
Though fan opinions vary on its quality, the Jedi Academy Trilogy plays a key role in the timeline of Legends novels set after Return of the Jedi. The series follows Luke Skywalker's mission to rebuild the Jedi Order by searching out Force-sensitive candidates and establishing a new Jedi Academy on Yavin IV. All does not go well at first, with a powerful Imperial superweapon emerging from hiding even as the spirit of an ancient Sith Lord works to corrupt the new generation of Jedi apprentices.

Buy on Amazon:
Book 1: Jedi Search
Book 2: Dark Apprentice
Book 3: Champions of the Force

This is a post-Return of the Jedi series from the Legends timeline. Think of it as an alternate universe from The Force Awakens and newer books.