There's not really a lot to say about this book - if you're interested in CoffeeScript, then it's great. It summarizes a lot of what CoffeeScript is about, the syntax, and is basically very good documentation on the language.
Personally my experience with CoffeeScript is pretty limited - in fact on a few projects where CoffeeScript was the default language for client-side code, I wound up writing JavaScript and then using a converter to convert it to CoffeeScript. The CS was definitely shorter, but I always found it confusing. There's something about the syntax that I just generally find baffling for some reason.
This book helped things make a lot more sense for me. The weird language and syntax quirks started making a lot more sense, and the weirdness around variable scope finally clicked for me. That said, I still prefer writing JavaScript to writing CoffeeScript, and I realize that makes me a cranky old man but it's true. This isn't really the fault of the book or anything but I felt like it's worth mentioning that it didn't make a "convert" out of me or anything.
Full disclosure: I was a technical reviewer for this book.