The Art of R Programming: A Tour of Statistical Software Design / Matloff, Norman

As the Cantonese say, yauh peng, yauh leng, which means “both inexpensive and beautiful.” Why use anything else?
R has a number of virtues:

• It is a public-domain implementation of the widely regarded S statistical language, and the R/S platform is a de facto standard among professional statisticians.
• It is comparable, and often superior, in power to commercial products in most of the significant senses -- variety of operations available, programmability, graphics, and so on.
• It is available for the Windows, Mac, and Linux operating systems.
• In addition to providing statistical operations, R is a general-purpose programming language, so you can use it to automate analyses and create new functions that extend the existing language features.
• R includes a library of several thousand user-contributed packages.
• It incorporates features found in object-oriented and functional programming languages.
• R is capable of producing beautiful graphics for your presentations, reports or articles.