Library (Super Mario Galaxy)

The library is an area first seen in the Wii game Super Mario Galaxy. It is completely optional, as there is no stars to be collected, therefore not counted in a 120 star playthrough.

Super Mario Galaxy
The library is in the game's hub world, the Comet Observatory. If Mario or Luigi were to enter, only a rocking chair holding a storybook will be present. When chapters to the book are unlocked, Rosalina will then read only the chapters unlocked by the player.

Super Mario Galaxy 2
If the player collects 120 stars, Rosalina will be seen reading another book. Luma will bring her Mario or Luigi's hat, and Rosalina will begin reading a book about Green Stars. This cutscene will grant the player with green stars scattered around all the different galaxies.