Since I am not an expert in Greek mythology I didn't know too much about the original Cupid/Psyche story. I did enjoy this story, although I found it dark and very heavy-handed when it came to Lewis' writing of his Christian beliefs. I found it interesting how he was able to work all of those into a story that took place before Christianity began. I also read a version of the myth that was closer to the original and am now interested in reading some more Greek mythology.
To me, this book spoke about having faith in the unknown (meaning the intangible) parts of religion and that someone's faith can be looked at as madness by other people who don't share the same faith. An interesting way to get that message across. I also liked that it explored the idea of the purity of love, whether we do things for people truly out of pure love in THEIR best interests or if our love is tainted by what we feel is best, either out of jealousy or our beliefs, etc. To me, if we are to love someone purely, we do not try to lead them away from their "divine nature" but should assist them in reaching it, which may be hard to do if it leads that person away from ourselves. Pretty heavy reading.
Definitely not written for children, as with the NARNIA CHRONICLES, although those are very heavily-laden with Christian messages as well.