Well, after sending an e-mail to Google Books help, I discovered the problem (WE THINK). I did not magically divine that you could ONLY upload ePubs through their Google Uploader tool. The tool, which is Java-based, had not been working so well on my Windows machine, so I had been uploading using the web form, following (foolish me) the instructions on the screen. At no time during the upload did the software say, “Hey. You know ePubs won’t work with this method, right?”
So anyway, I switched to the Mac, where the uploader tool works, uploaded “The Silver Circle” and “Green Fairy,” and we will see. It takes 24 hours for them to show up in the “these are your books” list, I guess. Will update you as events warrant.
(At least they haven’t yet bounced a check to me, so there’s that, still.)