I sent a question to Support last night and received the following late this afternoon:
Thank you for your email regarding your Barnes & Noble pre-order for a
title not yet published.
When you place an order through our web site, your credit or debit card
is authorized, not charged, for the amount of the order. This
authorization puts the funds on reserve, which most card-issuing banks
release after a seven-day period.
Barnes & Noble charges for the order only upon shipping. As the release
date of your title draws closer, we will submit a new authorization
request to your bank.
Please accept our apology for any confusion or inconvenience in this
matter. Thank you for the opportunity to clarify the payment
and click on the options that appear in the upper
right-hand corner to view information about your order.
We look forward to your next visit.
Customer Service Representative
Barnes and Noble