The Burp Suite documentation is the primary reference for this book, and it should be the primary reference for anyone planning to use Burp or even if you have been using Burp Suite for some time.
The primary source for all the Burp-related documentation has to be the documentation that is shipped with the product and what is present on the website:
You can always get the latest documentation online at http://portswigger.net/burp/help/.
You might prefer having a handy table of contents, found at http://portswigger.net/burp/help/contents.html.
All the help available online is also part of Burp Suite. You can access it using the Help menu:
The Troubleshooting page is always useful: http://portswigger.net/burp/help/suite_troubleshooting.html
The user forums on the website are useful when facing issues where the regular documentation isn't helpful: http://forum.portswigger.net/
A few video tutorials from the creators of Burp Suite can be viewed: http://portswigger...