First of all, gnuplot documentation should (must!) be included in your proper
gnuplot installation. Consequently, you will find on your hard disk these files:
gnuplot.gih — on almost all platforms: this is the file from which
the help commands get their help
gnuplot.info on Unixes
gnuplot.inf and gnupmdrv.inf on IBM OS/2 and eComStation
gnuplot.hlp on MS Windows
Additinally, you may have installed hypertext gnuplot.pdf documentation.
And definitely there is also the FAQ file with Frequently Asked Questions.
Official gnuplot online documentation
The following official documentation is available online:
Translations of various gnuplot documentation
are available.
Documentation and tutorials there are NOT maintained by the gnuplot
development team, and these translations are probably not up to date
— please check this yourself.
Gnuplot in Action - Understanding Data with Graphs
by Philipp K. Janert (Manning Publications, 2009) is now available in print. This is the first
book on gnuplot and provides a comprehensive introduction, from the basics to power features
and beyond. Besides providing a tutorial on gnuplot itself, it demonstrates how to apply and
use gnuplot to extract intelligence from data. It is available from
Manning Publications,
Amazon.com
and other booksellers.