I'm writing a book teaching people how to be better R programmers. I want R users to improve their coding skills and programmers from other languages to understand the unique beauty of R. To this end, as well as planning for a traditional printed book, I've been writing the book in the open at http://adv-r.had.co.nz. As I work, I publish the source code on [github](https://github.com/hadley/adv-r) and I encourage readers to contribute pull requests to fix mistakes and bugs. To date, I've received over 400 improvements from nearly 200 people. In my talk, I'll persuade you why "open" should be your default, share some of the lessons I've learned in the process of writing a book in the open, and show you a few things that I love about R.