My wife had one of these that I liked to steal, so I got myself a couple when they went on clearance. I'm typically a large. They are oversized, so I got a medium, but I wish I could have tried a large as well. The medium fits, and looks nice buttoned up, but is a little tight around the bum. This is totally fine for me, as I intend to wear it on walks around town, and wouldn't usually button it up anyway. When it's unbuttoned, it looks like the right size.
I plan to wear this to work in place of a cardigan in a business casual environment in a mountain town. It adds a nice amount of extra warmth and is nice and cozy. Perfect for fall.