There's a research paper in the texts section I wrote together with Ann Kristin vom Ort. But it's all German and stuff, so I don't know if it's any use to you. If you do speak German and are interested in gamification, it might be of interest to you.
We mainly reread and recontextualize basic Game Studies texts such as Huizinga and Caillois as well as Csikszentmihalyi and highlight connections to sociologic theories. We also question the usual approaches to gamification and try to identify viable alternatives without discarding the idea in general.