There’s a second set of four Mistborn books set later, but they follow different characters, since the core trilogy stands on its own. There are strong references to the core trilogy in them though.

I don’t like those books as much as the core trilogy, but they’re okay. They’re purposely more pulpy and less epic.

Sanderson is going to make two more Mistborn series, each set a bit further in the future. I don’t know how good they’ll be but that world isn’t done yet.

Sanderson has other books set in the broader shared universe. Stormlight Archives is the best-known of them, as it’s going to be ten 1000+ page books, with five out. There are some minor Stormlight/Mistborn crossover details in them.

I’d consider recommending Stormlight, but I am hesitant. The first two books are incredible. Up there with Mistborn, and more complex with characters you get really attached to. The third is still pretty good. The fourth and fifth in my view (and a nontrivial percentage of fans view) start to decline. So unless the sixth and subsequent books get better, I am more hesitant with recommending Stormlight.

Of all his countless books, his core Mistborn trilogy is my favorite because it’s a well-done complete epic tale from start to finish.