On average I’ve ordered from Amazon once a week for the last four years or so. Not just books, but power tools, toys, kitchen stuff, the whole lot. Given the volume of my orders I think their customer service is super great; it sets the gold standard for other companies. No other merchant online or offline has provided the ease and accuracy of ordering as Amazon does. Still, in my experience there are occasionally glitches that their email-bots can’t deal with, usually entailing a minor billing snafu. In these rare cases you need Amazon.com’s almost-secret real-person customer service telephone number. You won’t find it on their website. I once got it by calling 800 directory assistance. In any case, they make it hard to find because a call costs Amazon more, so you should jot down this number for those special moments when only a human will do: 800-201-7575.
Worth having someplace I know I can get to.