If you’re a web developer or designer ready to learn Ruby on Rails, this hands-on guide is the ideal way to get started. Rather than toss you into the middle of the framework’s Model-View-Controller architecture, as many books do, Learning Rails 5 begins with the foundations of the Web you already know. You’ll learn how to create something visible with Rails’ view layer before diving into the more difficult inner the database models and controller code. All you need to begin your Rails journey is HTML experience. Each chapter includes exercises and review questions to test your understanding as you go.
Not the best resource you can find to Learn Rails and this book specifically won't teach you Rails 5. It doesn't touch any of the Rails 5 features that make the news *cough* *cough* ActionCable or Rails API.
Either way, this is O'Reilly's take on the Learning Rails hype train that came from the Rails 5 release.
There are better books to learn Rails like the free "railstutorial.org" by M.Hartl or "Agile Web Development with Rails 5" by S.Ruby. One is free, other is in-deep Rails and very close to the actual development process, hence the Agile in the title.