How To: Absurd Scientific Advice for Common Real-World Problems is a book by Randall Munroe.
Randall explains that For any task you might want to do, there's a right way, a wrong way, and a way so monumentally bad that no one would ever try it. This book is a guide to the third kind of approach. It's the world's least useful self-help book.
The book is available from September 3, 2019. But already February 2019 he began promoting it in the xkcd Header text at the top of the comic. Since then, most of the time the header has been a promotion for the book.
A month before the release he made an entire comic about the book, not a real comic but a temporary one day comic: Disappearing Sunday Update