Is it possible to spend a credit on a book that is already in your library? I think I did that today because there is no clear indication in the purchasing screen or store page that says whether or not you already own a specific title like a certain major online bookseller does. It's a big flaw if there isn't protection from clicking to redeem a premium credit on a book that's already in the library.
Since there is no available purchase history, I have no way of knowing if I was so charge.
It shouldn’t be possible, when you are going to purchase a premium edition the listing on the volume page should read “PREMIUM”, and when you click it you should be redirected to the purchase screen.
However after you purchase it when you go to the volume page of whichever series you are purchasing it should say “IN LIBRARY”, and if you click it then you should just be redirected to your library.
If you believe you have been charged twice in error please send an e-mail to firstname.lastname@example.org they will be able to look into it further for you
I'd say generally not possible, unless some weird bug or glitch. Just tried it with 2 tabs open ready to redeem on Vol. 09 of Der Werewolf. First redemption went through fine, second gave an error:
The 'BookCopy' instance is not valid. Details: 'volumeId' is not unique
@Farmerdad Looks like I lied, after rechecking, even though it gave me the error it still ate the credit.
Emailed support and they reissued the credit and said they were taking steps to prevent this in the future.
Though other than doing what I did and creating duplicate tabs for the same volume before redeeming, it should be as Rahul-Balaggan said.
Thank you two for responding. I did end up reaching out via email to provide myself with piece of mind. I almost went there first but decided asking on the forum before asking on email would be a better course to take.