Elantris

Sanderson's debut novel, set on Sel. The city of Elantris was once home to radiant beings — ordinary people transformed into near-gods by the Shaod. Then the magic broke, and Elantris became a city of the damned. The novel follows three POV characters navigating politics, religion, and the mystery of what went wrong.

It's a standalone novel (with a short story, The Hope of Elantris, and the novella The Emperor's Soul set on the same world). As Sanderson's first published work, it's rougher around the edges than his later novels, but it showcases his talent for magic system design and satisfying endings.

Start here if you like: political intrigue, standalone stories, mystery-driven plots, or you want a shorter entry point into the Cosmere.