Much has been said about the art, sound and general fun of this game. Let me focus on the family aspect:
My husband and I picked this up because of the potential for co-op play. What we didn't realize was that our three year-old would be able to play too!
The game allows players to use controllers or the gamepad. And the latter, for most levels, has the option of playing a helper character who can manipulate the environment - 'tickling' the bad guys into submission, pulling levers, twisting dials, carving paths through cake, and so on. While my daughter sometimes struggles to work through the logic of some of the activities (some of them require a finer degree of hand-eye coordination that she's got), she was absolutely able to play through the levels in the first three or so 'worlds.' There's also lots of 'extras' in this game - scratch tickets to get bonuses such as a trophy-style room of monsters and extra levels. You can unlock extra characters, which was great fun for my daughter as she ordered us to test each one out.
Generally, this game is fun to play with a good mix of action and puzzle solving. It was elevated by the ability to include my young daughter as a contributing member of the team!