Compared to many other books written on these topics, this book has some advantages:
1) It is short. Reading 100+ pages will only take a few days. 2) It is entertaining. Throughout the book a todo app is developed by using the above mentioned frameworks: Rails and NodeJS. So readers can clearly see which framework achieves which goals. 3) Even if you are familiar with these frameworks, you can easily skip introductory pages (how to install, etc.), as they are really short.
Also, the book provides some URLs for people interested in learning more about certain technologies.