problem in title (is there a way to change the font in the book, or increase it?)
this is with unicode fonts off:

this is with force unicode font on:

better, but still not everything is clear what is written
resolution is 1920x1080

i think there definitely is a way to increase the scale of the book, look at the main page

Unfortunately, that's a Patchouli issue :(

You can change the scale of the book by clicking the two-arrows button on the landing page, on the left side.