I continue to try and expand my understanding of gamification concepts and recently read: Playful Design
This book is good overview of the design issues of games and gameplay. I was looking for a book focused on the application of game techniques in business and this is definitely not that book.
Playful Design does a great job covering the foundational issues of game design, but it is in the context of traditional gaming. The book is written from the perspective of maximizing the player’s experience playing the game and discusses the various reasons people come back for more.
The book is definitely worth reading as background material. It will help expand your view of how gaming can be applied effectively, since it covers a varied range of implementations over the history of gaming.