Originally Posted by Blossom
It's just something that happens when a book is entered into the KDP Select program. It's free for a little bit then it with be free for Prime only.
I didn't think they were in KDP Select because B&N and Kobo has them too, but when I looked them up only the first run of the pink series are available. This blue Eternal series must be KDP Select then... I'm all caught up now! lol