This book is called "Video Games" and it's an 'early reader' style book that's meant to explain games to kids in a rather generic way. Notice the generic type 'robots' on the cover, as well as the knockoff type Playstation controller. You can't really have much of a book about games without Sonic though! So he gets a profile (middle) and is also mentioned in the definition for "platformers" the game genre. That says about how you get the characters like Sonic or Mario to jump between objects, defeating enemies to progress through the level. The profile states how he is a Sega mascot, appears in games, books, comics & merchandise. It also tells about how he got onto "The Walk of Game" in 2005, which honors game achievements.