Just heard from the History Book Club with the opposite type of explanation -- overly wordy, form letter like this:
We wish to confirm that our technical staff has resolved the issue. Please try again and let us know if you have any more technical difficulties.
This is a one-size fits all and goes on to tell me to un-bookmark, un-favorite, delete all cookies and temporary files, restart my browser blah blah blah which has nothing to do with my original problem of my email/username already being "taken."
So I ignored the instructions, went back to the site, and it is, in fact, fixed so I'm getting four great books for $4, but of course, with tax, shipping and handling, the total comes out to $17.11.
However, it's solved for now.