ePUBs are Zip archives, and BBEdit supports editing them in place. So you can make a backup of the ePUB, open it, and then edit the files right in the disk browser window.
Or you can unzip the ePUB, edit the files, and then rezip it.
R.
--
Rich Siegel Bare Bones Software, Inc.
<
sie...@barebones.com> <
https://www.barebones.com/>
Someday I'll look back on all this and laugh... until they sedate me.