R in a Nutshell by Joseph Adler describes the R language (ArrLanguage).
http://oreilly.com/catalog/9780596801717 OreillyAndAssociates
Its an AnimalBook (in this case a bird).
This is a very worthwhile addition to the material supplied with the program itself and explains some things which are missing from other documentation. For example on a linux installation
R -g TK &
will run R in a separate window instead of on the command line.
It also gives details of how to connect R to Microsoft Excell (Windows).
-- JohnFletcher