For the last few years The Chang School, at Ryerson University, has been developing a series of open courses and open textbooks on various aspects of digital accessibility. The textbooks are based on a series of MOOCs RUN from 2016 to 2019, each book a course in themselves. About 5000 people have participated in the MOOCs.
Please help spread the word. And, take a copy of the books for yourself. They’re all Creative Commons (CC-BY-SA)