To user5994461 below, to whom I cannot reply:

In the CC license linked, the following text reads like making an ebook would be alright. The helper text on "remix, transform or build upon" says "Merely changing the format never creates a derivative."

just FYI for the future. HN will limit replies for a few minutes after a comment is made to kind of slow down the discussion and prevent flaming/arguing in the heat of the moment.

If you want, you can click on the "time" of their comment (ex "3 minutes ago") which will bring you to a page that you can always reply to (at least in my experience).

For this specific case, repacking a book in another format is 100% guaranteed derivative.

/No need to be a lawyer. That's covered in law case study 301 and 302.