This book is an awesome guide with more than 100 lenses to look at your game. Written by Jesse Schell a professor of entertainment technology for Carnegie Mellon University’s Entertainment Technology Center (ETC).
I like the concept of the lenses in this book, it let you look at your game from different angles to assure you have a fun game in the end. The lenses are summarized in orange boxes which makes this book an awesome guide through your process crafting a fun game. It’s like having an instructor on tap.