Allomancer Jak is a hilarious, pulpy, over the top adventure story set on the Mistborn universe (specifically the Alloy of Law time period).
It adds a bit of world building–specifically explaining how the Koloss have changed since the first era of the Final Empire–but mostly it’s just fun to read.
I’m especially amused by the numerous footnotes ‘written’ by the editor. It’s a bit annoying to jump back and forth on the Kindle, but worth it.