'One thing I used to do to make it easier to navigate was to make each chapter head a link back to the TOC.'
'So, I have no hassle with having an in-line TOC. Especially for short story collections.'
I prefer an HTML ToC as part of the book. With an inline ToC you can navigate within the book, you don't need a button of the device.
In my collection of short stories I have a backlink to the ToC at the *end* of each story. If you make the *head* of the chapter a link to the ToC you have to scroll back to the beginning of the chapter before you can click on the link. I think this is not so useful, especially if there are some pages to go back.