Gem Rush was the game I received this past month from Game Box Monthly, and we were able to break it out during the massive snowstorm we had recently.
What I loved about this strategy game is that it's not only challenging, it also has the option to be played either competitively or cooperatively. Now, my husband is very good at strategic gaming, so I tend to lose. The option to work together is nice because it makes it more fun, and it gives us a chance to enjoy the game rather than arguing about who may or may not be cheating (him, obviously).
Basically you are building a mine. Each mine room is constructed with gems, earning you points. You need specific gems to build certain passages, and getting gems depends on luck and strategy. In the competitive version, you fight to earn more points, and your strategy would be focused on making it hard for your opponent(s) to build and thus earn any. In the cooperative mode, however, things change.
This is how we played for this play through, and the mine is slowly collapsing. You must earn so many points before there are no more gems and you're trapped in the mine. We started at the lowest level - and still ended up only one turn away from losing! There were five cards left in our deck when my husband earned our last one-point token, and after my turn, we likely would have run out. This was a much more challenging game than we expected and we learned quickly that we needed to be very careful how we constructed rooms and how many cards we wasted.
This game was a lot of fun, but surprisingly challenging. I like that it is designed for people who play games, although it may be too hard for younger players. Since we don't have kids, though, we like a mix of family fun time and something a little more difficult. This was a refreshing chance to have fun with a bit more strategy involved.