I started reading
The Art Of R Programming, by Norman "I'm not Bernie!" Madoff. It seems pretty good, but I've put R learning on the back burner for now. It's an interesting language though. You expect a language reference to start with basic I/O, introduce variables, operators, go into branching and looping, maybe talk about functions and classes next. With R, the beginning tutorials are more like:
1. How to print out a
string
2. How to assign a variable
3. How to read in a CSV file, run a least squares regression on the data, and output a graph to a PDF.
Operators, if-else, and functions come later.