Is Insurgency: Sandstorm worth $20?

Is the came Insurgency: Sandstorm worth the $20 that it's on for the summer sale? I'm quite conflicted on whether I should get it or not for this price, I would like to know the opinions of others who have played the game. Is it a bargain to get it now or just not worth it at all.

Better to purchase first insurgency i think. I have 50 hours in it and still dont understand WHO THE FCK KILLED ME AND FROM WHAT PLACE