But once it does it totally rocks. It has some of the best characters, stories and ideas of any game ever.
A few tips to get the most out of it. I found it unplayable with mouse/keyboard... but a $5 dual analog usb gamepad was enough to make it rock. Also, the first level isn't the best in the game, and at the beginning you don't have many platforming powers, attacks, etc... so give it some time. Finally, make sure you explore the hub world and talk to all the other kids every chance you get... it's not essential, but it progresses all the backstories and makes the game much more deep, involving and fun.
Almost every level is unique, has a different art-style (all awesome), a different level mechanic and a different vibe. I won't spoil them by going into details.
One of the best games ever.