Since this book is full english, and have as subject the english language, let me try my best at a review in english.
So this book is, more a less, an essay about style, grammar and english syntax.
It's full of the details that make that language so funny to write. Indeed, as a french speaking person, I'm used to have some kind of formalizing body, the french academy, which role is to judge what is good or not.
According to this book, it seems like english does not have this chance and instead relies upon consensus. Obviously, this consensus is not always so consensual, and it looks like there are rules which provoke jeated debates amongst linguists, grammarians, and other language professionnels. This should make that book really appealing to anybody with a deep knowledge of english subtle rules. For me, unfortunatly, it was way too detailed.
However, I learnt a few very interesting things, even appliable in french. As an example, the need for valid sentences is explained in syntax tree browsing (which I find really appealing as an IT engineer). Moreover, there is a whole chapter about the way language tries to transform, through this syntax tree, our web of thoughs into linear sentences. And this is just the tip of the iceberg.
So if you want to learn how to write sensible english texts, this book is, even if I'm not the best to judge, a must-read.