Ruby (along with Python and Javascript) is a kind of a language that allows you to use it without dropping a sweat to study it. That’s what has happened to me. I’ve been using Ruby for a while, but haven’t read anything but blog posts about it.
This book gave me a good momentum to start using some of the Ruby features I (i.e. Fibers ) that I was completely unaware before, though the amount of input it provides is not overwhelming which helps you to digest this book over a weekend.
That’s a good starter for anyone willing to start coding in Ruby 2.1, lots of examples are outdated if you aim for Ruby 2.4+
My score 4/5