Bones of Empire - William C. Dietz
Second in the duology that started with At Empire's Edge- from the national bestselling author.
In a far-distant future, the Uman Empire has conquered and colonized worlds. Once thought invincible, its reign is now fragile as alien subjects and enemies conspire against it.
On holiday in the capital city, cop Jack Cato gets a glimpse of the Emperor-and realizes what he's looking at is a supposedly dead shape- shifter. His mortal enemy is still alive and once again on the run. And the fate of the Empire-and Cato's own honor-are at stake...
Zak Cato, #2