Here are the two I have for iBooks. I’m using NextDNS so it will still get blocked when I’m outside the house. I only read my local epubs so I don’t know if blocking these will affect anything you bought on the store.

  *.amp-api.books.apple.com
  *.p2-buy.itunes.apple.com

Thank you for this! I applied using AdGuard Pro and it works great

||amp-api.books.apple.com^ ||p2-buy.itunes.apple.com^

In AdGuard syntax, in case it saves someone time

Thank you!