3 stars because of the amazing art and fairly addictive gameplay, however I've taken off 2 stars because of how heavily it pushes real money transactions (RMT). This can ruin your experience, depending how deep in you've let yourself get and how strong your willpower is. There is virtually no limit to how much you can spend and some people do get hooked on this.
Exerting willpower has a chemical cost in the human brain. Fighting the often constant temptations of things to buy can wear the player down significantly so please take care of yourself if you think this will become an issue for you - this is true of any RMT game.
In saying this, it is entirely possible to play the game without spending a penny.