The Gamification of Learning and Instruction by Karl Kapp – http://www.amazon.com/Gamification-Learning-Instruction-Game-based-Strategies/dp/1118096347/ref=sr_1_1?ie=UTF8&qid=1460030413&sr=8-1&keywords=the+gamification+of+learning+and+instruction
Explore Like A Pirate by Michael Matera – http://www.amazon.com/Explore-Like-PIRATE-Gamification-Game-Inspired/dp/0986155500/ref=sr_1_18?ie=UTF8&qid=1460030700&sr=8-18&keywords=gamification
The Multiplayer Classroom by Lee Sheldon – http://www.amazon.com/Multiplayer-Classroom-Designing-Coursework-Game/dp/1435458443/ref=sr_1_22?ie=UTF8&qid=1460030745&sr=8-22&keywords=gamification
Gamify Your Classroom by Matt Farber – http://www.amazon.com/Gamify-Your-Classroom-Game-Based-Epistemologies/dp/1433126702/ref=sr_1_36?ie=UTF8&qid=1460031003&sr=8-36&keywords=gamification
More General or Corporate Focused(?):
Gamification Toolkit by Kevin Werback (he’s somewhat of an authority) – http://www.amazon.com/Gamification-Toolkit-Dynamics-Mechanics-Components-ebook/dp/B00VIH1ZOO/ref=sr_1_4?ie=UTF8&qid=1460030459&sr=8-4&keywords=gamification
For the Win (also by Werbach) – http://www.amazon.com/Win-Game-Thinking-Revolutionize-Business-ebook/dp/B009NFNVUE/ref=sr_1_13?ie=UTF8&qid=1460030459&sr=8-13&keywords=gamification
The Gamification Revolution by Gabe Zichermann (Gabe runs the annual Gamification Summit) – http://www.amazon.com/Gamification-Revolution-Leverage-Mechanics-Competition-ebook/dp/B00BDE6AKG/ref=sr_1_14?ie=UTF8&qid=1460030459&sr=8-14&keywords=gamification
Gamification by Design (also by Zichermann) – http://www.amazon.com/Gamification-Design-Implementing-Mechanics-Mobile/dp/1449397670/ref=sr_1_16?ie=UTF8&qid=1460030459&sr=8-16&keywords=gamification
Other Related/Valuable Resources:
The Art of Game Design: A Book of Lenses by Jesse Schell – http://www.amazon.com/Art-Game-Design-Lenses-Second/dp/1466598646/ref=sr_1_35?ie=UTF8&qid=1460030882&sr=8-35&keywords=gamification
Those resources are by people I know or have met. There are lots of other selections in Amazon. Kevin Werbach does a huge and vastly popular Gamification MOOC about once a year. It looks like some of the resources are still open/available (https://class.coursera.org/gamification-002/lecture).
Gabe Zichermann and Lee Sheldon have some good videos/TEDTalks on YouTube. Michael Matera and Matt Farber are K-12 Educators and active in Twitter Chats on the topic.