I read the Mistborn novels following my reading of Stormlight, and compared to the later I really struggled to get through them. They read more like teen-fiction in comparison.

There's been a stark improvement in his writing quality. The Stormlight Archive is much more robust in characters (granted the main protagonists can still get a bit angsty in places), incredible in terms of world-building (which of course is what Sanderson is really know for), and has a story line with enough plot twists and development to keep you entertained despite the page count.

I highly recommend it, but if the size of the volumes are bit daunting the Audible narrations are decent too. I flipped back and forth between the two, listening to it in the car and then reading from where the recording left off when I got home. I'm not normally a fiction buff, but I'm chomping at the bit in anticipation for the next in the series.

The 3 books total about 1.25 million words mind, so get ready for the long haul.

The general reason they're well liked is that they have deep and well thought out world building, while also being fairly fantastical. Characters aren't entirely realistic and sometimes parts of the books can drag, but they're true epic fantasy.

I'd still recommend Way of Kings to you, it's quite a bit different from Mistborn, and his writing has come a long way.