If you only buy one book before entering the world of self-publishing it should be Aaron Shepard's Aiming at Amazon. Even with the ability to update content in print-on-demand books, with all the changes at Amazon in the past 18 months, it is a bit much to expect Aaron to keep updating Aiming at Amazon every two or three months.
So Aaron has posted some changes and updates at his self-publishing website. All of the changes and updates posted are related to the content in Aiming at Amazon.
Here is the link: http://www.newselfpublishing.com/blog/#Aimingquickies