Skip Square's Sell as Pre-Order option
Square's Sell as Pre-Order setting requires a cutoff date, and the item comes off your site once that date passes. It also stays a preorder item after release instead of becoming a regular listing.
For books, leave that setting off. Create a regular item, note that it is a preorder in the name or description, and keep taking orders through release day and beyond.
How you handle inventory on that item depends on whether you have already placed the order with your vendor.
If the books are already on order, receive that quantity now
If the title is already on a purchase order, receive that quantity into Square with Track inventory turned on.
Square sells down from that number and stops at zero, so the on-hand count acts as a cap on how many copies you can promise.
Pro tip: hold off on titles that release next year. Receiving them now puts the stock and its cost on this year's books. Use the tracking-off setup below instead.
When the shipment arrives, the count in Square should already be close, since each preorder sale removed one copy from the total.
If you're still gauging demand, turn off inventory tracking
If you haven't ordered yet and want to see how many customers want the book first, create the item with Track inventory turned off.
Name it something like Preorder: Twilight and put the release date in the description. The item stays available on Square Online and at the register with no quantity on hand.
Avoid entering a placeholder quantity to get the item to sell. You would have to remember to zero it out before receiving the real shipment.
Count preorder sales in Square Orders
With tracking off, the orders themselves are your count. In the Square Dashboard, open Orders, search for the preorder item, and add up the line items.
A few weeks before release, use that count to place your vendor order, plus any copies you want on the shelf after publication day.
Those same orders are your hold list. If you also keep reservations in Edelweiss or Omnibus, copy them over from Square Orders.
Update the item when the shipment arrives
If you received the quantity up front, receive the shipment as you normally would. Tracking is already on.
If tracking was off, open the item in Square, turn Track inventory on, and remove Preorder: from the name. Set the quantity to the copies you received minus the copies already sold.
Where book by book fits
When you add an upcoming title through book by book, the release date is added to the top of the Square description, and the title is highlighted during review so it isn't shelved early.
The usual receiving advice still applies: wait to update Square until the shipment is in front of you. Receiving a quantity up front as a cap is the one exception, and only for copies you have already committed to buying.
Wrapping it up
The workflow is simple: skip Square's Sell as Pre-Order setting and create a regular item. If the books are already on order, receive that quantity now so it acts as a cap. If not, turn off inventory tracking, count sales in Square Orders, and order from that count. When the shipment arrives, turn tracking on and set the on-hand quantity to what is actually in the store.