|06:30 am - aha|
I really should have figured this out before now, but the postal "book rate" is now Media Mail. "Now" has probably included the last decade or so, I am guessing, which tells you how often I find myself mailing books. As opposed to ordering books and having them mailed, because I send people books reasonably regularly.
Anyway, I just had to laugh at my oversight. So much for being the cutting-edge early-adopter! Heh.