[pirl8]

Another idea...

Custom book reading font can be added without installing any hack, but the way they're shown in the "Aa" font dialog really sucks. First of all because they have to be (re)named to come lexicographically before the system fonts. Second, because the dialog is too short, and names in the third line are actually half-cut (and not shown at all in case of an AZW3 book with embedded font because of the "Editor's font" selectors).

Would it be possible to resize the "Aa" font dialog? Setting the height would be just enough. Maybe it could be added to the margins hack.

Edit: never mind... Adding exactly six fonts actually resolves the problem: no more unreadable lines. By the way, I wonder if enlarging the dialog it is possible to show more fonts...