Fanatical used to be known as Bundle Stars, and has Endless Space 2 as their "Star Deal" until the end of the day. Reputable site, I made many game purchases from them without a problem back when they were Bundle Stars.
Game will activate on Steam, and you save ~$5 off of Steam's price. Biggest problem is there are only a few keys left at this point.
As for the game itself, it's a good 4x space strategy game. I played it over the Steam free weekend a little while back, and didn't really want it at $20, but for $14 I didn't hesitate. Steam reviews are overall good. Feel free to discuss or leave your opinion, of course...