All books at the Hogsmeade Literary Festival have had a tracking charm cast on them. This helps the various store owners and their assistants ensure that no-one is casting any doubling or summoning charms, as these would greatly undermine the books' market values.
The inventory spreadsheet will be updated at least once a day or once every two days, depending on my own availability. If you notice any discrepancies following an update, please let me know.
View the Inventory