The premise is Nolan Garret is the assassin Cerberus. A former space marine called a Silverguard, he rids the galaxy of its worst scum for his employer. Unfortunately, Nolan is over a barrel as his brother is imprisoned for treason and his boss doesn't mind using that for leverage. Nolan's life becomes even more complicated when he decides to rescue a fellow ex-Silverguard, Bex, from an overdose she had on his very doorstep. Bex is the property of a local crime lord allied to his employers and things go south from there.
I really enjoyed the world that Andy Peloquin created here as it reminded me of a grittier, more down-to-Earth, Imperium of Mankind. This is a universe with super-advanced technology and space travel but all the horrible evils of today. People are addicted to drugs, local criminal organizations wield vast power over the public, and poverty is a bigger killer than aliens. I would technically classify this as a cyberpunk novel even though it involves a galactic empire. The fact it is full of strippers, street crime, and jaded veterans is a take I don't see often enough in my science fiction.
This is an incredibly action-heavy book with several chapters of a protracted assassination compromising the book's beginning. The action is incredibly fluid and actually contributes to the world-building as well as Nolan's characterization. Nolan is somewhat overly reliant on his A.I. partner and super-tech but there are times that he's stripped of both that allow us to see just what sort of soldier he'd be without them. Even so, my favorite parts of the book are the non-action parts as we see insight into the main character, his world, and his viewpoint.
If I had any complaints, I would say that Nolan is a bit too much of a tarnished paladin for his world. Despite being a former drug addict and assassin, he's probably the nicest criminal you'll ever meet aside from the Yakuza series' Kazuma Kiryu. I wouldn't have minded a few more vices from Nolan or some edge that would have shown him to be more flawed. On the other hand, he is a guy recovering from all manner of terrible things and he wouldn't be the same guy if he wasn't the heroic paragon he's trying to be. The fact there's a scene where he's tempted to go back on Blitz was really well done and one of my favorites.
I can't really understate how much I appreciate a big epic space story that has the stakes of warring street gangs, a woman ODing on our hero's doorstep, and revenge for a couple of people killed in the crossfire. The fact this is firmly street level despite involving a government conspiracy and interplanetary marines makes this feel different from just about everything else out there. My favorite parts of the Expanse series has always been the world-building among Belters versus the godlike protomolecule so this is just what the doctor ordered. Street level science fiction is something I can never get enough of.
In conclusion, Assassination Protocol is a really solid piece of entertainment and I already want to read the sequels. While it took a bit to get me to make a solid emotional connection with the main character, I was hooked the moment I was. Fans of science fiction, gritty crime drama, and big epic space universes will enjoy this. I purchased the audiobook version as well and think Bronson Pinochet did a great job. He has a deep drawl that adds a certain strength to Nolan's character.