There are some other great British crime shows that are season long mysteries. Best one is Line of Duty, followed by Unforgotten.

Endeavour is episodic but amazing.

There's one called Shetland that isn't that great but it has one season, I think 3, that is so good. It's about a convicted murderer getting released from jail, going back to his small town and the cops trying to figure out if he's involved with a new crime. You can just watch that season as a standalone.