[hbtaylor]

I did a little bit of digging. I decided to look at the EPUB contents to see if anything stood out. I'm a neophyte when it comes to EPUB innards, but I figured it would be a good learning experience.

I downloaded Sigil to take a look. When I opened 2 of the 3 books that were giving me problems, I noticed that they had nice Tables of Contents already. The third book had a one-item TOC, so I discarded it on the assumption that was just how the book was put together (without a meaningful TOC structure).

I decided to give Sigil's "Generate TOC" a spin, and did so for one of the books. When I uploaded that one to GPB, it had a good TOC! I looked at the other, and it had a nested TOC (but used h1 tags for all of them), and I didn't want to manually fix that up, so I thought, "I wonder what happens if I just open it and save it?". Sure enough, doing that made the TOC display correctly (nested and all) in GPB.

So, Sigil can do something to clear up the problem books. I know it is cleaning up and re-arranging, since the directory structure is different (created an OEBPS folder, moved the HTML files into a "text" folder, etc.), and I'm guessing something about that makes GPB like it more. I haven't dug in to specific differences to specific files (and may not, unless the mood strikes me), but it looks like I can open the EPUB in Sigil and save it back as a work around. I use calibre to manage my books, so I'll probably just save off an original_epub to be safe and try that.

If there is someone who is wise in the ways of the EPUB, they might be able to shed some light on why that save/cleanup has a positive effect.

h.b.