There is a fine line to walk while playing, whether it is worth following the rules and ruining lives or bending the rules at the risk of getting caught in order to help destitute people. The moral choices in the game are often difficult and require hard decisions.
Papers Please has a unique puzzle solving element. Instead of using mathematical logic, or quick matching thinking, the puzzles in Papers Please involve checking people's background information to make sure everything matches the immigration requirements and following clues to find anything amiss.
The gameplay itself, once the player gets a grasp of it can get repetitive pretty quick due to there really being not much deviation from a singular gameplay mechanic.