I recommend you start with our JCGS article to get a sense of what ESS does and why. An earlier version of the article is in the ESS distribution as file ess-5.3.2/doc/ess-intro-graphs.pdf The manual is in the ESS distribution as file ess-5.3.2/doc/ess.pdf The reference card is file ess-5.3.2/doc/refcard/refcard.pdf