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52 minutes ago… comics and manga, which is another aspect I’ve been noticing calibre does not do such a great job
Absolutely. Calibre is horrible with anything that is fixed format. I recently backed up my entire Kindle library with about 1k manga volumes, expecting to be able to convert from KFX to EPUB format as I have been doing for my regular books for 15+ years. Calibre failed awfully at this. The only thing it’s reasonably good at with comics, is converting to ZIP format. So I had to write a Python script to take the KFX -> ZIP outputs from Calibre and convert them into working EPUB files.
Most of my ebooks are large as they are comics. You also have EPUB3 ebooks now, which can contain images and audio in them too (think combined ebook + audiobook). So they can get pretty large.