Incidentally, I wonder if you can answer a question: I want my books in an electronic format, that will be usable for the rest of my life or longer, and which preservers annotations.
As far as I know, PDF/A is the only format that fits the first two specs. I know annotations are in the PDF specs but is it reasonable to think that annotations I make today will be readable - and updatable - in (e.g.,) 30 years?