Star Wars: Allegiance
by Timothy Zahn
Hard to say too much without spinning off into a complete reiteration of the story. Zahn really owns Star Wars - he created the Thrawn trilogy, and invented characters and races that have spun off into independant existence in the Expanded Universe of Star Wars fiction.
Some SW novels are more like fantasy stories that is okay, but not my preference. Better are the authors, notably Zahn and Karen who Traviss, have a way of starting with the (extensive) universe of Star Wars details and writing something much more like capital"H" HARD nuts-and-bolts science fiction. This effort follows four different but related scenes - a group of honorable storm troopers who have deserted, Mara Jade, the Emperor's Hand who is investigating deception against the Empire, Princess Leia, off on a diplomatic mission, and Han, Luke and Chewie investigating piracy problems. Lots of action, and interaction between these four scenarios. A great book - one I expect I'll re-read - probably even buy when it comes out in paper.
(addendum - I meant to note that this book reminds me in some ways of the stories of Lois McMaster Bujold - particularly the Warrior's Apprentice
and Miles's improvisations compare to the stormtroopers scrambling to figure out what to do.)