One vendor replied immediately, saying they should have been there by now, and gave me a refund, saying the book was mine to keep if it showed up. The other vendor did not reply.
Both books arrived via Media Mail today. Both wrapped identically in really cheap-looking fibrous brown paper constructs big enough for a hardcover book, kind of vacuum packed - the process looks like glue is applied to the edges of two flat pieces of heavy paper, the book is placed on top of one piece, in the center, and a press frame pushes the other piece down on it from the top, sealing the pieces and possibly pushing out excess air. Cheap and artless.
Looking at the invoices, the one which gave the refund says they received the order on 7/6, but did not ship until 7/17. The other lists the order date as 7/17, which is bogus. In any event, both sellers waited 11 days to ship a book, media mail, knowing it can take a month for the USPS to deliver. Shoddy.