If you notice any mistakes, and don't want to fix them yourself, open an issue on the Github page of the book.
If you are reading this book with GitBook, you can also create a quick inline comment.
Making contributions while you are reading is a good way to learn faster. If you have a hard time understanding something, try to reword it and make a pull request for other readers.
You can also help fixing issues. (Protip for university students: a good GitHub profile is more valuable than a diploma in the job market.)
For every donation on this address, you will appear on http://n.bitcoin.ninja/.
The book on GitHub
The book on GitBook (You can download pdf, epub, mobi versions here.)
Code examples on GitHub
Hall of the Makers (Here are the true makers those succeeded to complete the challenges of this book.)