Well, all I know is what I've gleaned from the books, i.e. 1st Edition 1976 Doubleday & Co. Inc., Garden City, New York. It was apparently published in UK at the same time, by Souvenir Press, also hard-back, but with a different dustwrapper (I've never seen one though). The first paperback edition in the UK was by Fontana Books (1977) and then Heywood Books published the one we've seen above in 1989. I'm sure there were others in between, so we ought to be able to put together a full printing history, not forgetting the German and no doubt French and other versions.
I've often thought it would make a good film, as it has all the ingredients (action, romance, intrigue etc). Better material than 'Zoya' anyway, although that was made because it was a 'Danielle Steel' bestseller, whereas our author Robert Tyler Stevens (not his/her real name) is completely unknown. I've tried to find out about him/her, without success. Can anyone help? I wonder if it was written by a man or a woman? And if it was made into a film, who would we want to play Olga and her family, John Kirby, Princess Aleka, and the lovely Karita? Here we go again....more questions beginning with 'What if...?' !!