I'd like to begin by saying that I've read this book twice. The former was simply a read-through, and the latter was to collect notes. In my opinion, this book is an essential guide, but it is also difficult to read for a few reasons. There is plenty of vital information in here for anyone interested in design, and it covers multiple countries such as Britain, France, Germany, USA, Japan and more. Furthermore, there are multiple styles included, and it contains a number of designers (I calculated somewhere around 336, give or take a few).
However, upon finishing my notes, this was an immediate gripe of mine, given that I'd whittled it down to only 57 designers being noteworthy; with the rest being one-time name-drops, assistants, or otherwise being barely mentioned. I remember my first read being confusing because of this overwhelming number of designers being sprinkled throughout the book; not in any biographical, or even chronological manner - but rather just dropped here and there. It made me paranoid to think that if I didn't remember a name, it'd become important later on - but it seldom was.
Another gripe I had was the organisation of dates. Something about the way the dates were laid out makes it disorientating, in that it dances back and forth between eras. For instance, you'll be jumping from chapters such as: "Avant-Garde and the Origins of Modernism 1914 - 1940"; straight to "National Tendencies until the 1940s"; to "The United States in the 1930s"; and then back to "War and Propaganda 1920s - 1945". I understand that graphic design is multi-layered, and not everything can be lumped together; but layout like this can only ever make it difficult to mentally map out where everything is in relation to all else while you're reading. This is *truly* a book that is for reference and note-taking, not for understanding the subject via reading alone.
Amongst all this, the tone is documentative, very dry and humourless. I also couldn't help but to feel bias from the author in favour of Modernist design; since traditional German & British design is somewhat skimmed over in favour of Bauhaus & Swiss Modernism, despite the book itself making it clear that the latter was not the norm for the times in question. It's not as though I don't understand the importance of Modernism in design, but a large enough portion of the book is so dedicated to covering it, that it feels like a drag at times due to the lack of variety.
Overall, it's not as though the information in this book is false or unreliable, and it certainly is a must-need read for anyone interested in the origins of design. The context and information itself is well-researched and documented, and I respect the author for having gone through the pain of collecting it. Sadly, however, the aforementioned was enough to put me off of ever reading this book a third time.