Darth Vader and Emperor Palpatine flex their Force muscles in Paul Kemp's Lords of the Sith, but the real stars of this book are Cham Syndulla and his rebellion on Ryloth. According to the publisher's summary:
On Ryloth, a planet crucial to the growing Empire as a source of slave labor and the narcotic known as “spice,” an aggressive resistance movement has arisen, led by Cham Syndulla, an idealistic freedom fighter, and Isval, a vengeful former slave. But Emperor Palpatine means to control the embattled world and its precious resources—by political power or firepower—and he will be neither intimidated nor denied. Accompanied by his merciless disciple, Darth Vader, he sets out on a rare personal mission to ensure his will is done.