Does anyone know what fairy tale "Ever" by Gail Carson Levine is based

Question: Does anyone know what fairy tale "Ever" by Gail Carson Levine is based on!?

I'm just assuming its based on something!. Ella Enchanted and Fairest both were and Ever has a similar design!. I just can't figure out what this one is! It's making me so frusturated!
I first thought it was Sleeping Beauty, but reading it, I don't think that's it!. I looked at all of the other fairy tales I've read, but none of them fit!.
Will someone help please!? :)
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Best Answer - Chosen by Asker:

http://www!.gailcarsonlevinebooks!.com
The link above is good, and safe, and one place to read lots about this book, as well as others and the author and all that good stuff!. But!.!.!.

http://www!.amazon!.com
It is from reviews at Amazon that I learn that most people feel this book is based not on fairy tales, but on Greek and Indian myths!.!.!. Olus = Greek, Kezi = India/Indian!.

*You know how to see reviews at Amazon!? Separate your book by clicking on it, then scroll down past the publication info and other books for sale, and you're there!. Reviews can also be expanded on the right!.

*I thought of them both as partaking in the myth of Orpheus, who travels so hopelessly to the land of the dead to bring back his love, Eurydice, also known as 'Agriope!.'

--I had to find that name Eurydice in the source below, which also gives me the fact that the Orpheus myth was/is world-wide, even called "Akkadian/Sumerian" (Middle East I'd say)!.!.!.BUT 'Akkadian' also matches a name used in "Ever!."--
http://en!.wikipedia!.org/wiki/Orpheus
This is a fun question; thanks!.
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