Just sign in and redeem a key, free for the next 48 hours. Never played it but it looks alright.

Game description:

X-COM: UFO Defense is provided via Steam key for Windows. For key redemption, a free Steam account is required.

You are in control of X-COM: an organization formed by the world's governments to fight the ever-increasing alien menace.

Features:

Command deadly close-combat battles

Shooting down UFOs is just the beginning: you must then lead a squad of heavily-armed soldiers across different terrains as they investigate the UFO crash site. Tackle the aliens with automatic rifles, rocket launchers, and even tanks in the struggle to retrieve useful technology, weapons or life forms.

Research and manufacture alien technologies

Successful ground assault missions will allow X-COM scientists to analyze alien items. Each new breakthrough brings you a little closer to understanding the technology and culture of the alien races. Once you have sufficient research data on the UFO's superior weapons and crafts, you'll be able to manufacture weapons of equal capability.

Develop a strategy to save the Earth

You must make every crucial decision as you combat the powerful alien forces. But you'll also need to watch the world political situation: governments may be forced into secret pacts with the aliens and then begin to reduce X-COM funding

store.steampowered.com/app…60/

- ostinato

Also included in the free purchase is a 10% off Humble Monthly coupon:
"10% off Humble Monthly for New Subscribers Only
Expires 3 Mar 2017, 18:00 GMT"
It makes buying the Humble Monthly that includes XCOM 2 £8.89, OR you could use the coupon for next month's bundle (given the expiry date)...
- EQL