It's interesting to see functional programming concepts through the lens of JavaScript. The book does a good job of explaining the fundamentals in a clear, concise and hands-on way.
I also like that it's pragmatic and advocates using the right abstraction for the problem at hand, which dependent on the problem can also mean an object-oriented approach. That's how I currently mostly value functional programming, as an additional tool/technique on my tool-belt, rather than something that replaces most of it.
Since I've already spend some time in F# and Clojure the book was more of an refresher to me. I think it is a good starting point though if you're interested in functional programming before you actually go on and read a book on F#, Haskell, Clojure, et al.