The best game I played in a while.
The gameplay itself isn't that challenging except for the boss battles. There are side missions that will earn you money to buy upgrades, such as increased damage with your weapons. This is good when you are playing through the game but when you finish and go back to the first few missions to collect coins the if you get in a fight it is too easy to win because your weapons are maxed out.
When I first started playing I was told that the game is short (mostly by reviews). So I was expecting it to be over quick, but thats not the case the game is decently long, not so long that you get bored with it but, long enough that you spend some decent time with it, and master the srt of assassination.