My DevOps books are free in April, thanks to Device42!
Last month I announced I was going to make my books Ansible for DevOps and Ansible for Kubernetes available free on LeanPub through the end of March, so people who are in self-isolation and/or who have lost their jobs could level up their automation skills.
The response floored me—in less than two weeks, I had given away over 40,000 copies of the two books, and they jumped to the top of LeanPub's bestseller lists.
Purchases (over 99% with price set to 'free') of both books spiked within hours of the announcement.