I'm the author of both this and the PragProg book (
http://pragprog.com/book/tbcoffee/coffeescript). I wanted to offer a more succinct guide to the language that would quickly address common points of confusion. My hope is that CoffeeScripters who hit some unexpected behavior will be able to open the iBook to the right page, tweak a code sample, and say "Aha!"
Caveat emptor: This is a first edition, and updates (both technical and content-wise) are planned for the near future. Feedback is very welcome.