Thanks Frank - I have also noted that iBooks Author can export to epub. I think you access this by using an epub template.
I have been testing out a few options before I invest a lot of time in the project so that I am less likely to have to change course later. I am converting an anatomy book into an ebook for a doctor friend and I have the original word documents that were sent to the printer for production of the hard copies. The content is largely text with illustrations and photos. My requirements are to publish to Apple and Amazon.
I would prefer to have one product that services both sites and is generic enough that it will probably be Ok for any future e-publishing that I haven't thought of yet. Also I am a mac user. I also want the internal structure of the ePub to be simple and consistent as that is likely to make it layout consistently on devices that I can't test on.
The conclusion to my tests is that for my purposes I will follow this workflow
1 - Follow the guidance of this paper Creating ePub files with Pages - Apple Support
and load the recommended template into Pages.
2 - Import the word documents into pages
3 - Reformat the text using the styles from the template and reset the pictures
4 - export as an epub from pages
5 - As I am OK with html and css, I will inspect the results by opening the epub using an application called Sigil.
I noticed that when I followed these steps the contents of the epub were nice and simple as I had hoped. If required I can make small adjustments in using sigil.
I also tested importing the word documents into iBooks Author and choosing an ePub template and then exporting to epub, In this case the contents of the epub were much more complex with apple specific elements. My preference for simplicity have caused me to conclude that iBooks Author is not the tool for this job, however others may have different requirements and a different process may well be better suited for them.
Please comment if you think I am missing something.