It has a lot of potential, but...
I purchased Endless Space recently, having heard interesting things about it & being in the mood for a good 4X game. The game does a number of things well- the graphics are pretty (especially for an "indie" game), the atmosphere is great, the menus have a nice, clean aesthetic, and the first couple dozen turns of exploration are magnificent.
Unfortunately things start to fall apart in some fundamental areas of the genre. Even with the tutorial mode enabled, many game mechanics remain frustratingly opaque. How many turns or food does it take for my planet to gain a population point? Why does the game always remove population from my most useful planets when settling new worlds in a solar system? Why does expansion inexplicably make my citizens unhappy, when one of the reasons for their discontent is "overcrowding"? I'm no stranger to Civ-styled games, but I do expect them to avoid including pointlessly vauge systems. Unbelievably there is no in-game 'Pedia- instead the help menu hotlinks you to a fan-run Wikia page, which is useless when you simply want to find out why your borders won't expand (or what borders even do).
The most serious offense however is the dreadful combat system. You design your own ships, based around some combination of missiles, kinetic weapons and blasters, plus related defenses. What makes one type of weapon better than the others for what situation is unclear. Battles are decided by drawing three cards, one for each phase of the battle, and each card has a certain in-battle effect. That's fine, except cards counter each other, and seem to have little relation to their own text. A card which boosts kinetic weapons but lowers your defenses will still win you battles if you play it at the right time with a fleet using lasers. Invading planets is an inexcusably boring affair, camping above worlds for dozens of turns while the computer throws endless waves of ships at you. Stalemates are inevitable & the AI hates peace, even if you're ever-so-slowly grinding it to dust. I personally gave up in disgust when, after having taken two core worlds from an AI & blockading a third while I spent two dozen turns capturing it with a giant armada, it destroyed my entire military with one turn remaining with an enormous top-of-the-line fleet apparently pulled from its ass, settling me back hours of play.