The more professional option is to buy your own ISBNs and “publish” the book under your own publishing imprint — this is relatively straightforward if you already have a business entity, but requires setting one up if not, which obviously carries an accounting and admin burden You’ll use a different ISBN for each format (e.g., hardback, paperback, Kindle, iBooks, etc.) and each new version (only for major updates, minor fixes don’t matter)
