Many web programmers, especially Angular programmers are turning their attention to Reactive programming. While I don’t know of any books on ReactiveJS (yet) I can shamelessly mention that I do have a book on Reactive Extensions and LINQ.
NB: This book is short (which I think is a good thing) and pricey, but will give you a solid introduction and more to both topics.
My co-author, Paul Betts, is not only a genius, but he is one of the foremost experts on Reactive.
Here is the TOC: