Zak Cato Books in Order

The Zak Cato books are built around a lawman in an empire that talks about order more easily than it delivers it. The setting is the Uman Empire, a sprawling future state that rules many worlds and keeps a close watch on alien species that were never fully willing partners. To manage that tension, it relies on the Xeno Corps, bio-engineered officers trained to detect, pursue, and if necessary kill dangerous nonhuman threats.

Cato is one of those officers.

That makes the series part police story, part military thriller, and part imperial intrigue. The first book starts with a prisoner transfer involving a deadly Sagathi shapeshifter. When the mission goes wrong, Cato ends up isolated, disgraced, and forced to hunt through a local political mess where almost nobody is telling the truth. The second book widens the frame and digs deeper into the question of who really controls the empire, and whether the system Cato serves is stable or already compromised from the top down.

One thing that gives these books their own flavor is the alien politics. The Sagathi are not just monster-of-the-week antagonists. Their history, containment, and relationship to imperial power matter to the plot. So do the worlds Cato moves through, because Dietz likes frontier planets where corruption is practical, local rulers are opportunistic, and a single arrival from offworld can upset a shaky balance.

The tone is tougher and more suspicious than heroic. Cato has duty and skill, but he is not standing in a clean moral system. He is trying to do the job inside a structure that may be using him while hiding its real problems. That keeps the books moving beyond simple chase scenes and gunfights, even though there are plenty of both.

If you want science fiction that mixes investigation, alien threat, and empire-level conspiracy, this is a good corner of Dietz's work to try. Start with At Empire's Edge and continue straight into Bones of Empire, because the second book deepens the first rather than resetting the board.