This add-on seems to do a very good job, but sometimes leaves blank spaces where there should be text.

Since there's no telling what text it has missed out, that effectively makes the add-on unusable.

See, for example, the GNU Grub manual: https://www.gnu.org/software/grub/manual/grub/grub.html

Epub creator creates an epub of this page with blank spaces where there should be code snippets in section 2 (called: "2 Naming convention").

It produces blank spaces instead of code snippets for some of those that appear in section 3 (called: "3 OS-specific notes about grub tools"). And yet it reproduces other code snippets on that page faithfully. At a glance, there is no obvious difference between those snippets it reproduces and those it cannot.

So the add-on is unusable. It omits some text, and it's not possible to know what text it's missing.

I gave it three stars for effort. Because it looks like a job well started but not quite yet done.

UPDATE:

The same problem is apparent in Firefox Reader View. So it seems to be a problem with Firefox, not with the add-on.