When using Book Proofer (available from iTunes Connect for iBooks) to test EPUB folders or EPUB documents in iBooks for iOS, entries in iBooks’ native TOC will not link to their respective document if the name of the source EPUB folder or EPUB document contains spaces.
Note that this issue has nothing to do with names of files inside the EPUB, but with the name of the zip or folder that contains the whole EPUB structure.
When using Book Proofer (available from iTunes Connect for iBooks) to test EPUB folders or EPUB documents in iBooks for iOS, entries in iBooks’ native TOC will not link to their respective document if the name of the source EPUB folder or EPUB document contains spaces.
Note that this issue has nothing to do with names of files inside the EPUB, but with the name of the zip or folder that contains the whole EPUB structure.
Tested with an EPUB 3 folder with name "EPUB 3".
Seen on iBooks for iOS 3.2 & Books Proofer 1.0.1