I played Space Siege as a result of a random Steam Roulette spin, and I was blown away by how great of a game it is!
The game revolves around the invasion of a race of aliens known as the Kerak, who are bent on the elimination of the human race.
The game is top-down, and plays somewhat like Diablo 3. The story is fantastic, with hints of Mass Effect, Dead Space and Deus Ex: HR. Those who enjoy those games will probably love this.
The game is a little old, it was released in 2008, and the control system is definitely a little dated. Everything else is generally great, but if you are going to play I would highly recommend you ensure that you had a way to use the keybinds ingame (especially Map, Health Pack and "Collect all loot", these are imperative). Sadly, the game has no method of rebinding keys, so this might be a chore. I use a Razer Naga and bound the imperative keys to the sidebuttons and it worked like a treat.
I can't emphasise this enough, this game is fantastic! It took me 8-9 hours to fully complete the game, while collecting the sub-story Data Pads, and loved every minute of it. Again, if you liked games such as Mass Effect, Deus Ex: HR, Dead Space, with the playstyle of Diablo 3, you'll enjoy this game a lot.