Allegiance - Timothy Zahn

A Star Wars novel set between the events of Epsiode IV: A New Hope and Epsiode V: The Empire Strikes Back, it features a younger Han, Leia, and Luke, as well as Mara Jade.

Mara Jade, the Emperor's Hand, is looking into the illicit financial affairs of a planetary governor, hoping to find evidence that he might be funding the Rebellion. Luke, Han, and Chewbacca are sent on a mission to help some rebel supporters. Leia is busy being a diplomat, trying to drum up support for the Rebel Alliance. And a band of 5 stormtroopers, on the run after refusing a direct order, finds itself in the strange position of doing good deeds...and perhaps even aiding the Rebellion.

The paths of all of them will crisscross back and forth as they come closer and closer to meeting up with one another...but never quite managing to.