Troy Denning: Star Wars: The Joiner King (Dark Nest I) [2005] paperback

Seven years after their daring assault deep inside enemy territory (Star Wars: The New Jedi Order: Star by Star), Jaina Solo and her fellow survivors answer a mysterious call for help and vanish into the Unknown Regions.

Soon, the Jedi Council learns that the group has undertaken a mission that will drive a wedge between the Galactic Federation of Free Alliances and its skittish ally, the Chiss Ascendancy. The investigation leads Luke Skywalker and his companions (Mara Jade Skywalker and Han and Leia Solo) on a perilous journey into the uncharted void that lies between what is right and what is wrong.