There have been a number of space station sim games over the years, but in the past most have been firmly of the tycoon game style--that is, primarily about building modules and expanding your station, with some notional flow of dollars increasing if you do it well. SpaceStationSim takes a somewhat different approach; it's more of a hybrid of a life sim (the granddaddy there being The Sims) and a tycoon game. You create an astronaut, and the gameplay involves both building out your station and satisfying the needs of your crew. Which includes, naturally, things like making sure they have enough to eat and time for potty breaks--and also enough to breathe. Life on the final frontier isn't always easy.
It's interesting reading over some of the reviews SpaceStationSim has received over time--it was originally a commercial, in-the-stores release from Enlight--because some take it to task for its alleged difficulty, while others think the tycoon aspect, at least, is fairly easy. (Which it is, at least once you learn what the various modules you can add do, and how they inter-relate with each other.) It sometimes seems like the reviewers are playing different games--which, perhaps, they are: Bill Mueller has been tweaking the game periodically since its initial release (it's now up to version 2.1), and has made it rather more newbie-friendly over time.
You'll most likely be interested in SpaceStationSim if you're a space buff and like the idea of operating the International Space Station; while this isn't a hardcore simulation, it is based on data from NASA, and does a good job of portraying the station visually, with some nice elements of verisimilitude, including the need to keep the many contributors to the station (the European, Russian, Japanese, and Canadian space agencies as well as NASA) happy.
But from the perspective of a game design aesthete, this game holds considerable interest as well: since the release of The Sims, I've been expecting developers to build on its basic paradigm to produce a whole genre of "life sim" games, but with only rare exceptions (e.g., the, ahem, Playboy game), this hasn't happened. SpaceStationSim shows how some of the concepts of that game can be fruitfully applied in a very different environment.
Given the title and nature of the game, you'd expect a self-consciously serious and perhaps even dour sim; actually, SpaceStationSim is charming, and even a tad humorous at times.