I really like the Adafruit tutorials and I use them. Sometimes though, the tutorials skip over some important information that "everyone knows". As a high school teacher, I have learned that if you start assuming even a minimum of knowledge, you can loose your students in a dense fog.
Yesterday I found this free downloadable book: ASKManualRev5.pdfhttps://docs.google.com/file/d/0Bw_ruMO ... edit?pli=1
From what I have read, I like the explanations of code commands and how they work.
The pdf states that you are free to use and distribute the book for non-commercial uses as long as it is not modified.