Star Wars: Lost Battalion

Leia's diplomatic vacation to a spaceport controlled by criminals and villains goes awry when Luke Skywalker is apparently killed in a trap set just for a Jedi.
Luke, using the cover of his apparent death, takes R2-D2 to a mysterious planet. Rumors suggest it may be the very origin of the Force.
With assassins around every corner, Leia and Han must watch their step while trying to reign in the lawless spaceport threatening the trade of nearby New Republic planets.
Against the greatest power Luke has ever faced, he must prove himself worthy, or never leave this mysterious planet.

Set after Jedi Academy Trilogy book Champions of the Force in the Star Wars Legends universe