It is what it says it is.
The game itself has quests from different people delivered in the form of e-mails.
They'll have different needs to be met but a lot of it is straight forwards.

I wish there was a little more story to the game and a better way to organize the emails.
There isn't much replayability as once you're done the campaign, you're done. Playing through a second time doesn't change anything.

You do get access to your own personal tanks which you're able to set on free mode so you don't have to worry about feeding if you really want to freestyle. There's one achievement that takes 7 irl days to complete (it's honestly not that bad) but it did suck since I'd finished the game and had nothing else to do. If you play through this game I recommend doing starting this achievement right away and then playing through the campaign slowly over the 7 days so you at least have something to do.