Yes, this book is one I recommend to anyone who wants to really understand functional programming. Admittedly it's not Haskell, but it's the book I wished I'd had back when I first learn FP (and Scala).
It lost me about 2/3 in when it got to monads.
That's OK. You've already learned more than enough. My life in Scala was just fine once I understood that a monad was just a data type that admitted a flatmap operation.