Getting started with R was a bit of a challenge. I almost gave up: sure, I could struggle through most problems and eventually get the job done, but the experience was frustrating. I finally came across the pdf of this book, and immediately ordered the print version. The authors of this book managed to include the most important details to help an R beginner without burying them in unnecessary minutia. I sat down with this short book over a weekend, worked through it and came away with a solid foundation in R. I almost immediately started understanding how R "thinks." Once that foundation is in place, it becomes very natural to use R, and very easy to learn about features and packages not covered in this book.
Yes, this book is available as a free pdf. Such generosity on behalf of the authors certainly shouldn't be punished with low ratings as some reviewers have done; they should rate the content. Since the book serves as a tutorial, it is much nicer to have a physical copy sitting on your desk (especially if you only have one screen).