Should you buy this game? If you are looking for a "game", then no. The Story of a Star isn't a game in that sense, you are not gonna find a lot of interaction, or deep, evolving strategies. It is more of an experience. There are things to discover and to unlock, yes, but the primary point of this application is to create a new experience, letting your mind interpret what is happening.
The Story of a Star lets you partake in the life and death of a solitary star. What will happen within this small part of the infinity that is space? Will there be life? Will there be peace? Or war?
Unlock the different stories being told, and watch the star reach it's ultimate fate.