Now I have a somewhat better idea of exactly what I have to do to cope with the new Amazon policy. It's not terribly pleasant, because it means raising prices solely to feed Amazon, but unfortunately if I want to sell via Amazon, I have no choice but to play by their rules.
Amazon has changed the way it handles on-demand printed books, like ours, and as a result most of them are only available from third-party merchants, or with a 2-3 week delay. They are still available from Book Depository (within free shipping) normally, and I don't expect that to change.
We can fix the problem, but it requires making new print data for all our books and registering them with Amazon's own in-house on-demand printing subsidiary, CreateSpace. The books will have the same ISBN, price and content, but they will be handled by two different printers depending on where you order them from. Needless to say, it will also take time and money to convert all our existing books over to the new format...
It's a royal pain, but unfortunately Amazon has absolutely no obligation to sell our books if it doesn't want to, and we have no choice but to comply... which we shall be doing over the next few months.
Please accept our apologies for the problem, and we hope you'll stay with us until we get it fixed.