As an apology, we’ve decided to include an extra copy of the book for every copy you pre-ordered. We’re very sorry about the inconvenience- but hope that freebie books is considered an adequate compensation for the hassle.
It’s more than just a nice apology — it’s smart.
Everyone who pre-ordered is probably a fan. Who will be getting a spare copy of the book. Which they’ll give to a friend.
Despair turned an error (which customers probably wouldn’t have noticed) into a a fantastic word of mouth opportunity.