Gronk: Caveman Detective: The Case Of Temporal Chaos!. Gronk: Caveman Detective, #3

Gronk is a caveman. Gronk is a detective. Gronk does not ask for any of this. When a far-future Imperium: imagine Rome, but without the falling part, scaled across galaxies and powered by twenty-five thousand centuries of uninterrupted conquest: discovers time travel, they do what empires always do with new territory: they send someone to take it. That someone is X7, a temporal operative carrying technology that shouldn't exist and orders that don't include "ask nicely."The target? Gronk's timeline.
A world where civilization is still figuring out plumbing, justice is still mostly bonking, and one undersized caveman with a talking rock and a stubborn sense of right has accidentally become the only thing standing between the Stone Age and total erasure. Armed with his trusty Small (a rock, but an opinionated rock), backed by the towering builder Thunk and the quietly unstoppable Grep, Gronk must unravel a conspiracy that spans realities, face down a conqueror literally named Kul, and save a civilization that hasn't quite decided if it wants to be saved.
The Case of Temporal Chaos! is the third book in the Gronk series: a genre-defying blend of prehistoric noir, space opera, and the kind of deadpan humor that makes you laugh, then makes you think, then makes you laugh again because thinking is hard and laughing is better. For fans of Terry Pratchett, Douglas Adams, and anyone who's ever suspected that civilization was a questionable idea from the start.