First, don't buy it from Apple. Search for the same eBook in another Store. Best as ePub.
Load it in http://calibre-ebook.com/download_osxhere you can make changes and you can edit them.
Then convert it in calibre to HTMLZ (a zipped html), the problem now is that the Mac is unable to unzip this. So you need an additional Software like the Unarchiver from here http://unarchiver.c3.cxor direct from the MacApp store.
Another possibility is to convert it in the newest Calibre as .docx (is brand new) and then you can easily edit them and now convert it with https://itunes.apple...422235937?mt=12to a .html or http://Jutoh.com. T his creates a cleaner .html, than if you save it in Word etc. as website.
Now import it http://accordancefil....htm#kanchor406
Unfortunately Accordance doesn't support links and cross-refs, colors etc.