Can I use this Windows 10?

Solution
It's a real copy. I bought a copy from Amazon (probably from that page) for a build I did a couple months ago.

Elaborate on these mixed reviews you're referring to.
It's Amazon and they have a good return policy. I physically screwed up the product key (scratched too hard) on my first copy I bought and Amazon replaced it immediately. If Amazon will replace in that situation, they'll replace it if you get a key that's been used.

Buy with peace.