Well - the ebook format(s) are a pain.
- They're not sufficiently standardised for all parties to agree on.
- The quality of tools to create them is rubbish.
- And interoperability is a pain.
It's like web in the early days, different interests trying to subvert html, trying to "embrace, extent, extinguish". It took almost 20 years for the web to settle down around well understood common and open interoperable standards.
The epub format is open but still in flux. Amazon doesn't actually support it properly or directly - with lack of support in places, inconsistent support elsewhere, and additional proprietary features too. They have their own mobi, kf8 and azw formats too. And now kpf too. Their preview tools all work differently too - showing different results.
This is depressing - especially as it should be possible for all Kindles, old and new, to show text, follow basic links, and show images. Except they can't. Some do, some don't.
I felt bad about some users not being able to read the book properly .. so I had to act.
The new Kindle Textbook Creator works more like PDF - a format that preserves layout but at the cost of not being able to reflow text.
I made the decision that it was more important for the book to always work for readers - even if that meant fewer readers could buy the digital book. Older Kindles can't buy the book now it is in the new format. I am sad about that.
One day, digital book publishing will be fixed, or as fixed, as the web is today.