This book reads like a stream-of-consciousness first draft.
The giveaway is the endless repetition. Why do we need to be told THREE TIMES that Martin Luther posted his 95 theses on the church door at Wittenberg in 1517 and that this was a seminal event in the beginning of the Reformation? Why do we need to be told TWICE that in Wittenberg alone, 100,000 copies of Luther's translation of the Bible were printed during Luther's lifetime? Why do we need to be told THREE TIMES that the 30 Years War devastated the German countryside and made life miserable for the peasant population? And those examples are just from one chapter; they are representative of an endemic problem.
Then there are the issues of the content itself, which the previous two reviewers have discussed. It seems to me that in a book purporting to be the biography of a language, it would have been useful to include more examples of that language as it evolved than this book has. It certainly would have been more relevant than the mini-biography of Luther's wife or the details of exactly when the major Lutheran church bodies in the United States got around to disassociating themselves from Luther's excoriation of the Jews. The author tells us, several times, that High German is so called because it developed in mountainous southern Germany and Low German because it prevailed in the lowlands of the north - yet gives just a single, one-word example of the sound shift that distinguishes the two languages. The author talks about how Luther in his Bible translation combined his local dialect with chancellery German, but gives not a single example that illustrates this.
A good editor would have caught these things. This book clearly did not have one, or perhaps it had one but the author was not willing to accept the editor's advice.
I give it three stars because amid all the chaff, there is some wheat, especially for someone like myself who is trying to relearn German a half century after studying it in school and who is curious about the history of the language. But the book could have been, and should have been, so much better.