For me this was too much geared to American students who look at people who speak two languages as if they had two heads. I also found that the descripions of specific language situations to be oversimplified. (Most 'German' speakers in Switzerland have four or more varieties of German to deal with, not two, as radio and television tend to use the Zurich dialect, and Swiss standard German is noticably different from the standard German spoken and written in Germany and Austria.) I was also rather surprised to read that multilingualism was not an issue in medieval Europe except maybe for clergy. I just don't think that is true.
Whatever. It is positive that there was felt the need to have a textbook like this. It is certainly not the last word on the subject. ( )