This is not a "fun game". It is, however, an excellent implementation of the dual n-back system that has been shown in actual studies to improve fluid intelligence.
When you first start playing the game, it can be extremely frustrating. But if you keep it up. You will improve, and the game becomes easier—at least until you progress to the next difficulty setting. From my own experience with playing the game, my ability to recall information that Ive read or heard (on a short-term basis) has seemingly approved.
The developers have done a great job designing an simple but still attractive user interface. They have also included an excellent tutorial mode, which should make the rules of the game, which can seem confusing or counter-intuitive until you see them in action, obvious.
If you are looking for an app with addictive gameplay, you will be disappointed by IQ boost. But as Ive already mentioned, IQ boost, does not seem as though it is supposed to be a fun game in the traditional sense. The dual n-back game is a real mental workout—according to the studies results at least— and playing IQ boost feels like real mental exercise. Like a a real workout, IQ boost is tiring, when your timed session is over (the studys authors measured fluid intelligence increases when subjects played the game for 20 minute sessions) you will be ready to do something else. But like a real workout, the results should make you smile