Following up the indications for confounding variables we uncovered the complicated situation of genre in this subfield of the literary market. We succeeded to explore some of its substructures which haven’t been described yet in literary studies, though it has been always one of its topics that this kind of literature is a commodity (Nusser 1973, Nusser 1991, Nutz 1999, Stockinger 2018). It is quite astonishing that almost every genre behaves differently, but this may be the result of a decades-old competition between this small number of publishers. Probably the different structures correspond to different strategies of each publisher. Bastei-Lübbe for example seems to follow a strategy where each series has a distinct profile, while Cora is focussing more on the publisher name as brand (Fig. 7 and Fig. 4) - though the clustering may also be influenced by the fact that Cora translates many novels from English. It would be an interesting follow-up-project, to find out, whether the readers of these genres know about these structures and how this knowledge directs their choices. Last but not least, we think that the strategies to control for known and unknown confounding variables in text classification, especially if it is done to understand existing structures and not so much to predict really new data, needs to be explored in more detail.