Birthday promotion

Today is my 42nd birthday. Help me celebrate by getting Object-oriented Programming in R for only $1 and the current draft of Meta-programming in R for free. On Amazon you can still get The Beginner’s Guide to GitHub. This will change at some point today but then I will start a new free book promotion right after, so if you want it free you might have to wait a day or two, but it will be free again.
So wish me a happy birthday, sing me a song, and leave a review of one of my books on Amazon or Goodreads.