Started this one months and months ago! But the thing about Grammar books is that you don't usually read them start to finish. This will be a great reference work, but it is set out in a way that makes it quite hard to read more than a few pages at once.
What this is not: this is not a guide to teach yourself German. It is wrongly set out for that purpose, for a start. Early chapters go through all the structures of German sentences that can happen, but I think it was not until chapter 10 that we finally had a discussion of word order that made sense of all those structures.
There are exercises and chances to practice what is presented, but if a student were handed this book and nothing else to learn German, I don't expect they would get very far.
Still it is a thorough grounding in the grammar of the language, and having read it once, I hope I will feel confident to go back to those sections that I only have a hazy recollection of to try to really get to grips with the grammar.