This is a great game for 12 bucks. Been playing it non-stop since I picked it up last weekend. The shooting mechanics are spot on and so is the loot game. It's like a mix between Halo, Borderlands and Warframe. Has 3 person coop and open world exploration with a linear story mode. For 12 bucks it is really really good.
If you do pick it up remember that the humble monthly is a subscription. So make sure you unsubscribe immediately so you dont forget and get billed next month.
Also, as a bonus you'll get something like 6 more games in 2 weeks (dont know what they are yet though until they release them.)
I highly recommend Destiny 2 though if you liked any of the 3 games listed above.
p.s. remember if you do buy it. The monthly is a subscription. SO immediately go into your humble account and unsubscribe so you dont get billed again next month.