For the next 4 days you can play Killing Floor 2 for free. This is a good opportunity to try it out and see if you like it before you commit to buy. If you want to buy, it is 50% on Steam at the moment. However, please check other stores such as Humble, GOG, Gamersgate etc. to see if it is offered cheaper there. I have not done that check. I merely mentioned the 50% off deal for the sake of completeness because if I had not mentioned it I am sure the first comment would have been to include that.