Fury by Aaron Allston

This book continues to tell the story of Jacen's fall. He gets even more protective of Allana, to no avail for his own plans, while Jag, Jaina, Zekk, Han, and Leia track down Alema Rar and Luke decides to support the Galactic Alliance, but not Jacen. Jacen gets even worse as a character, so it's going to be easier when he's eventually defeated, but I'm still generally frustrated by this plot line.