Books are not dead. I believe there is a great opportunity for specialist to "distill information" in their field and offer it to others as books. People don't pay for the content (which can be found on the Internet) but for the analysis and the curation of this content.
It's not "easy money" because writing and editing a book takes years of sustained effort, but if you're an expert in X, you already spend your days explaining X so writing down your explanations won't be //that// tough.
[1] noBS guide to Math and Phys: http://minireference.com/ [2] https://gum.co/noBSLA
PS: Anyone interested in writing a book about Chemistry and/or Biology? Get in touch with me so we can combine forces and take over the UGRAD textbook market!