Well, actually I gave up at 38%, not because the book is bad, much to the contrary, it is an excellent introduction to an excellent framework, but for my current work and ideas Akka is not (yet) relevant. I may change my mind, but for now I am done with the book.
My only complaint is about the writing style. It's full of narrow cultural references that make sense (I assume) if you are American, but that rather occlude instead of enlighten if you're not. Have an example?
"Threads are an incredibly expensive resource to just start spending like you're dealing with Brewster's Millions", and in a footnote he writes ""Yeah, it was a pretty bad movie, but I was a kid when it came out, so it was awesome".
Well, in this case I know what he means, but unfortunately there's much, much more of that and it tires me. On the other hand, as I said, it's a didactically excellent tutorial. If Akka is what you want to learn, this is your book.