My review will start after this small disclaimer:
-Unlike the PC version, where you can walk literally for hours, and the world is almost never-ending, this console version isn't! The world is not that big, you could run from one end to the other in about 15 minutes, where you then come across invisible walls! :( Because of this miniature biomes are usually squeezed into one map, taking away the feeling of a huge world. If you have never played the PC version, then this probably won't bother you, you'll probably think that the world is huge. Bear this in mind before buying.
Minecraft is a game limited only by what you can imagine. It's like being in one giant Lego set of never-ending bricks. It's basically about doing whatever you want. The game has no linear campaign, no kind of story, or even any mandatory objectives, yet it is still very enjoyable. The only problem with having no story is that after a while you begin to realize that the game doesn't really go anywhere, you just build things.
So it looks simple, but underneath it's quite complex.
If you feel like a challenge, you can play in survival mode, where you'll have to build a hut [monsters come out at night] find food, build weapons etc.
Or if you're the creative type, you can play creative mode to build a big castle, a large house, a skyscraper, or anything else you fancy.
Children will love this game, and quite a lot of adults will too. You can play splitscreen with 2-4 people on one console [HDTV required], or up to about 10 people online.
I'd definitely recommend this game, it will kill hours of spare time!