On http://floss.booktype.pro/csound/preface/ you can find the online version of this book. This is the printed version 3, corresponding with the Csound Floss Manual release 6.
The goal of this manual is to provide an easy-to-read introduction to Csound. It is intended as an introduction-tutorial-reference hybrid, gathering together the most important information you will need for working with Csound in a variety of situations.