I have released my book I Love Ruby in epub format. You may get it here
I will discontinue the e-book edition on Amazon here
https://www.amazon.com/dp/B07NGY8PZ5 , as it forces me to enter a cost for
a book that can be distributed free of charge.
I would be very happy if people can send me feedback and suggestions to
improve this book.
Karthikeyan A K
Author of https://mindaslab.github.io/I-Love-Ruby/