One of the challenges that people must face when starting to learn radare is getting to know how to use it for their specific needs; after all, not everyone uses radare for exploitation or forensics. As mentioned before, radare is indeed documented.
If the difficulty is not related to a lack of documentation, then where does it originate from? There’s no middle ground between experimenting with each command in radare and replicating the writeups that people post online for often difficult challenges they solved. Beginners will often find themselves stumbling between understanding how radare was used and the task itself.
This was the motivation for writing Radare2 Explorations, a relatively short, free, open-source book which covers radare from a practical point of view, rather than a pedantic one.
Its purpose is not to replace the already existing Radare2 Book, but rather to complement it. You can read it online or download it as PDF, ePUB, MOBI, thanks to Gitbook.
What does it cover? All the basics required to get you going, plus a few tutorials which are focused on how to solve very simple but specific tasks using radare.
The introductory section is somewhat linear, although you can easily read the topics that interest you. The tutorial section is completely modular and each tutorial is a self-contained experience.