Seems like it started as a dlc idea for Super Mario 3D and just got stretched out into a "full" game. If you played Super Mario World 3D you will have a good idea of what the levels will be and how the game will look and sound. There are 3 books full of levels plus a Bonus book. Along with the main goal of collecting a star, each level has 3 gems to collect, gems unlock more levels, as well as a certain challenge to complete. These challenges vary from finding a hidden gold mushroom, to collect "x" amount of coins, and sneaking by Shy Guys. Each level also has a time challenge, but after playing each level multiple times already to do the other challenges, you may find it hard to want to go back and replay some of them again in hopes to shave a few seconds off your time. Along with the puzzle levels are "Boss" levels, either a dragon (Draggadon) or bird (Wingo). In the Draggadon levels the giant dragon will spit fireballs out while you climb up the puzzle volcano to defeat him. In the Wingo levels you will try to climb the puzzle tower while the bird flaps his wings to create gusts of wind to try and knock you off the tower; when you reach the top of the tower you will have an actual boss fight against the giant bird, where you throw giant turnips to defeat him.
Levels are unlocked in the Bonus book by completing the other 3 books and the various challenges within them. If you have a save file from Super Mario 3D you will also unlock 4 levels from the game. Besides the Mario levels, all of the bonus levels are rehashed from the other books, with added twists; such as levels where you need to find the rest of the toad brigade and move to the goal as a group of 4.
Could add more to the game, like a level editor and a way to share levels through Miiverse; Level pack dlc would also be a nice plus, if priced right; maybe unlocked with the Amiibo addition that is to come.
Overall a very nice game, but just again it just seems a bit short. $40 for a little over 10 hours of gameplay; come on Nintendo, you are better than this. 7/10