For experienced programmers, Advanced R will serve you as an excellent resource
to learn about specific aspects of R in a comprehensive manner, in addition to
digging through the individual (and wonderful) documentation entries inside
of R.
Getting through the book requires experience with R to make sense of it, so it
may not be the best place to start. However, an experienced programmer will have
questions that only this book addresses directly and easily. As such, using it
as-needed for reference is a fine approach.
Arrrr