The process of writing textbooks is still very traditional regarding the status of authorship and expert opinions. Recently we observe the emergence of authors who follow a different approach, taping the wisdom of crowds as key resource of their own publications. In this paper, we explore business model innovation which leverages value propositions of textbooks by applying crowdsourcing. We use case study research methods to analyze four textbooks written collaboratively. Essential findings indicate occurrence of user-communities fulfilling peer-reviewing, editing or co-authoring despite a lack of monetary incentives. We further detect a tendency towards wiki software providing a community hub. This paper enters the field of partially crowdsourced textbooks and derives future questions of research.