At the time of writing, there are three pie chart packages listed on the genchart topic: pgf-pie (which uses pgf/tikz), piechart (shell and AWK scripts to generate pie-charts expressed as pstricks code) and piechartmp (which uses MetaPost). The pgf-pie package is available on MiKTeX but is not on TeX Live.3 The piechart bundle isn't available on either MiKTeX or TeX Live, and only comes with a README file dated 1998. The piechartmp package is available on both MiKTeX and TeX Live, but requires writing MetaPost code which hasn't been covered in this series of books. In addition to these packages, the datatool bundle comes with the datapie package, which can be used to display pie charts from data stored in a datatool database.
Since the datatool package has already been introduced in this book, §12.2.1 The datapie Package discusses the datapie package. If you don't want the additional overhead that comes with the datatool package, §12.2.2 The pgf-pie Package discusses the pgf-pie package, but TeX Live users will have to install the package manually.
This book is also available as A4 PDF or 12.8cm x 9.6cm PDF or paperback (ISBN 978-1-909440-07-4).