Petri Lankoski and Staffan Björk have edited a book titled “Game Research Methods: An Overview”. Since I’ve been giving advice to students about conducting game-related research, this might be a precious (and free) resource. From the official page: “This book provides an introduction to various game research methods that are useful to students in all levels of higher education covering both quantitative, qualitative and mixed methods. In addition, approaches using game development for research is described. Each method is described in its own chapter by a researcher with practical experience of applying the method to topic of games”.
Download the ebook for free at http://press.etc.cmu.edu/content/game-research-methods-overview