Timothy Zahn 
Star Wars: Dark Force Rising 
(Thrawn Trilogy, Book 2)

In this essential Star Wars Legends novel, the sequel to Heir to the Empire, Grand Admiral Thrawn’s sinister plan threatens to spell doom for the fledgling New Republic and its most iconic heroes.The dying Empire’s most cunning and ruthless warlord, Grand Admiral Thrawn, has taken command of the remnants of the Imperial Fleet and launched a massive campaign aimed at the New Republic’s destruction. Meanwhile, Han Solo and Lando Calrissian race against time to find proof of treason inside the highest Republic Council-only to discover instead a ghostly fleet of warships that could bring doom to their friends and victory to their enemies.Yet most dangerous of all is a new Dark Jedi, risen from the ashes of a shrouded past, consumed by bitterness, and scheming to corrupt Luke Skywalker to the dark side.