Recommended reading
Books
For the Win (Kevin Werbach and Dan Hunter): http://wdp.wharton.upenn.edu/book/for-the-win/
Reality is Broken (Jane McGonigal): http://janemcgonigal.com/my-book/
The Gamification of Learning and Instruction (Karl Kapp): http://karlkapp.com/books/
A Theory of Fun (Raph Koster): http://www.theoryoffun.com/
How Gamification reshapes learning eBook http://elearningindustry.com/how-Gamification-reshapes-learning