Book 2 of the Hand of Thrawn series.
The Empire's master plan is under way. The New Republic is on the verge of civil war and the rumor that the legendary Admiral Thrawn has returned from the dead is rallying the Imperial forces. Now Luke Skywalker, Han Solo, Princess Leia, and their allies face the challenge of their lives. They must infiltrate a hidden fortress filled with Imperial fanatics, rendezvous with a double-dealing Imperial commander, and journey into enemy territory to learn the identity of those responsible for an act of unthinkable genocide. But most important of all is the truth about Thrawn. In his hands--alive or dead--rests the fate of the New Republic.
694 page paperback novel by Timothy Zahn