@GeoffR: Definitely a kepub, and not the only one like that (mostly from Hachette, AFAICT)

(flagged as KOBO EPUB in the UI, no adobehost process run, bearable pageturn speeds, and kepub font rendering, so I'm fairly sure of that

).
But yes, I am indeed using the nerfed kepub margins patch (default values)

.
Good point on the f's though, I'll check

.