You should better ask to Google, but this is what I found

Refunding Books on Google Play

You may return an eBook for a refund for any reason if we receive your request within 7 days of purchase. Purchases through Google Play for Education are refundable within 30 days from the day of sale. No refunds are provided for purchase cancellations of books sold for limited access periods of 24 hours, unless the content or service is defective. If the ebook does not perform as described, you may return it for a refund at any time. Refunds will not be granted in situations of purchase abuse. When a refund is granted, we'll remove access to the eBook and your money will be returned.

More info/Source: https://play.google.com/about/books/user-policies-for-google-play-books.html?visit_id=636749967209231514-1931612528&hl=en&rd=1