Minecraft is the best-selling game of all time. That alone should be enough to convince you, but here's some more information on why you should start playing right now. It is a sandbox game where players have to mine and build to create their own ideal world.
The game is simple: you start with your hands and limited resources. You start mining and collect the raw materials / materials you need to make tools and build houses and other buildings.
Raw materials range from very common to extremely rare and often those rare things are the most difficult to reach / obtain. Often you will need to dig deep for this, or even build reinforced tunnels to keep them from flooding with water or falling rocks.
There is no storyline, it is totally up to you what you want to do / achieve. You can build cities or a farming village. You can keep sheep or go fishing. The game is exactly what your imagination wants it to be.
Buy your key for Minecraft now and you can download the game directly from the developer's site.