Eh, I think my method is easier. You don't need to worry about cancelling anything if you don't process the order through ABE at all.

Unlike eBay and Amazon, who make it very difficult for you to give your private email address to a buyer (in order to negotiate), ABE puts you onto private communication with a buyer the moment you use ABE's question function. I usually want to ask a seller something anyway, so naturally a discussion of price comes up after. After the item is sold the seller doesn't have to do anything but remove the listing from ABE; which is perfectly normal --they could have sold it at a book fair or something.

Plus, if you buy multiple items from anyone using any of the above sites, none of these really cope with postage adjustments for packing stuff together; not an unreasonable expectation for a buyer to have.

BH