Recently I’ve got a few free books from PACKT and as one to read I chose Clojure Reactive Programming by Leonardo Borges. I’m already familiar with most of concepts and libs described in this book, but I guess it’s a good book. The book explains Rx extensions and usage of them from Clojure and ClojureScript, explains core.async and React (and Om), so I think it touches all aspects of “reactive” (such a buzzword). And coolest part of this book is appendix, it about library design but with functors and monads.
So summing up everything, this book is a bit for newbies, but great.