When I finished my university in 2013, I wrote my thesis about Rx and also released it as a free ebook available for anyone interested in learning about it. That book was written in Hungarian, it was based on Rx 2.x version and it was aiming Windows 8 WinRT app developers. Since then some things have changed in the library (moving to NuGet, changed namespaces, etc), Windows 10 (UWP) got released and I had the chance to rethink some parts of the book and most importantly translate it to English.
This book is not a hard core deep dive book, it's an introduction for beginners who want some easy to understand "Hello World" level examples to see the various operators working alone and combined.
I host this book on GitHub with the source code of the examples and any tools I've been using to put this book together, and I absolutely welcome any suggestions or requests to expand this book with, or potentially even do a series of blog posts or another more in-depth book to talk about more advanced scenarios.
I hope you are going to enjoy it.