Rating: 6.4/10.
Not quite what I was expecting — I was looking for a linguistic overview of the German language, but this book is more like an intro linguistics textbook that uses examples from German. About 70% of the material is general linguistics knowledge (eg: explaining what’s a phoneme or morpheme or word class), only 30% is specific to German. The book quickly covers a very broad run-through of all the major linguistics subfields (historical linguistics, phonology, syntax, semantics, pragmatics, sociolinguistics, etc), so it never has a chance to cover more than the bare basics of each field.