This book written to provide clear and concise explanation of topics for programmers both starting to learn the Ruby On Rails programming as well as those diving in more complex topics. Most examples are linked to online playground that allows you to change the code and re-run it.
The Ruby Hacking Guide is a book that explains how the ruby interpreter (the official C implementation of the Ruby language) works internally. To fully understand it, you need a good knowledge of C and Ruby. This book is going to investigate ruby as a whole.