For the price, you'll get (on average) six games each month – all unknown until the moment they're released. Here's how it breaks down:
1 "hot title" game that's less than a year old
1 "highly-acclaimed" game that's one to two years old.
1-2 hit indie games
1-2 "hidden gems" from developers
(Source, seems like they removed it now, here's a link to the webarchive)
I don't like preordering, but in this case, you get Grimrock 2 for basically 50% off, and I'm guessing that they'll probably have a bunch of actually good games the first month to lure people in.
Thought this said 'legends of grimlock'