Unlike many open source products, QGIS is blessed with a comprehensive, well-edited, and printable manual in the form of a PDF file downloadable from the QGIS website. In addition to this official manual, there are numerous tutorials and "how-to" documents, available as PDF files, web pages, or web-based videos, that are accessible through the Internet. A dedicated group of bloggers also contribute periodically to the growing body of "how-to" tutorials.
This diversity of information sources reflects and meets the needs of the growing base of QGIS users. This section is a compilation of the various resources about QGIS.
The QGIS Manual is available from the QGIS manual download page here (or click the image at right).
The download is for QGIS 1.7 PDF English version. By the time you are reading this, there may be a newer edition of QGIS and its manual available.
This is the comprehensive basic manual that covers QGIS and its built-in functions and built-in plug-ins. There is very little documentation contained herein for 3rd-party plug-ins.
The sole published English-language book (that I know of) containing a significant amount of coverage and tutorial materials on QGIS is The Geospatial Desktop: Open Source GIS & Mapping (2012, Locate Press) by Gary Sherman. (Gary Sherman is the founder and original developer of the QGIS project.) This book teaches desktop GIS using open source tools. It is an update of a 2008 book entitled Desktop GIS: Mapping the Planet with Open Source Tools, now out of print.
In a video interview released in early October 2011, Gary Sherman stated that he is also working on a separate book on QGIS. At that time, he indicated that he hoped to complete the manuscript by the beginning of 2012. However, that project has been put on hold as the fast pace of QGIS development would render any book instantly obsolete at this point. The team will re-evaluate the situation once QGIS v2.0 is released, probably in 2013.