Although published late last year, this book was just brought to my attention: Total Engagement: Using Games and Virtual Worlds to Change the Way People Work and Businesses Compete by Byron Reeves and J. Leighton. The book's site is here, and there are also a number of book excerpts. The Amazon site also has a 'look inside' link.
We connected with Byron Reeves at Stanford a number of times and reviewed his Seriosity work, which also has a blog. And is active on Twitter. Some of Reeves ideas were also inspirational for our early online advisory work.
Have not read the book yet. It's on my stack now.