If it's a knit, it kind of fits with the long cardigan way of looking at things. I'm short (5'4") so I usually avoid longer Jackets in that below hip and above knee range. But I got a longer blazer from Allsaints this summer and have been wearing it a lot. It tempted me to try this other long topper from NAS, and I'll be interested to see how it works out. All this to say, definitely try it and show us how it looks.

I would style & wear it as a long blazer. Sometimes you sit in your blazer & sometimes you take it off. Test sitting in it for a bit at home with clothes underneath to keep it clean & tags on & see how creased it gets.

ETA: I'd definitely look at all of Sveta's outfit posts with her fab grey gilet for outfit inspiration. The gilet is sleeveless of course, but the same kind or proportions would apply, and Sveta has been doing some brilliant looks with it (both office-appropriate and casual).