For some reason I found it hard to finish this book.
Three words come to mind: superficial, redundant and obvious. This, rather than a book, felt like a long, long blog.
Okay, maybe this review is biased since I have been myself professionally trained in data visualization, but this book felt unusually worse than others I've read.
Sometimes I was simply learning the names of things I was already doing, other times I wondered if I actually needed a book to explain me that. Also, some graph problems might've been exaggerated, in my opinion.
This said, there are also a few positive things to mention. For instance, I think this is a good reference point to guide my plot design thoughts, and there are indeed many examples of good graphs.
Overall, I think I did learn a couple of things, but it wasn't exactly a pleasant reading for me.