Hi Robert,
We are currently working on a new Wix app that will allow anonymous cancel and reschedules, this will give you the option to split the policies time and give the client a page that will allow him (or not) to cancel/reschedule. It will be released in a few weeks.
If you still want to implement it now, I would suggest creating a dynamic page that will be created for every book, the link for the dynamic page (unique per book) will be sent in the confirmation email (triggered email) to the customer, once the customer opens the page the code will check the policy of cancel / reschedule and show cancel/reschedule button accordingly, once the customer clicks on the relevant button the button will initiate the request for the specific book (cancel or reschedule).
Hope it helped, if not share your email and I will DM you.
Zvi