The most basic tier will get you
Outland: Special Edition,
Fallen Enchantress: Legendary Heroes and
Mercenary Kings. Beat the average—currently $4.81—and you'll also get
Endless Space: Emperor Edition,
The Stanley Parable and
The Incredible Adventures of Van Helsing II.
At the very top end, you can pay $18 or more to get
Space Engineers added to the mix.
There's some good stuff there. The Stanley Parable is excellent, and Endless Space is a decent 4X strategy—albeit not quite as good as Amplitude's follow-up, Endless Legend.