Wonderful...
Five is Not enough stars..
It's the best...
It's not about the BDSM and that being a right thing because it's definitely not or about him being a Billionaire. It's about him being attracted to her enough to not even realize he is in Love with her and wants something besides just the BDSM and he doesn't realize that he is already in Love with her after first meeting her. He realizes how empty his life is because up to the time of meeting her he has not understood the true meaning of love. Because of his past his having a bad Mom who is a crack addict and then cruel stepfather's and beatings and torture then his Mom dies and he has to be in the house alone with her body before anyone finds him at the most tender and fragile of ages. Even when he ends up being adopted he does understand how to Love because he can't let go of his past/childhood & the Elena years. Then worse someone like Elena comes into his life and he was already terribly confused because of his childhood. And then what Elena tried to teach & tell him that BDSM was normal. Once he meets Anastasia he wants to have real Love and he realizes how futile and worthless the BDSM really is. He is beginning to realize You don't treat someone you love in that way. Anastasia teaches him all of this because she teaches him to communicate, how to understand his feelings and deal with his past. And I think she falls In love with him at first site. And then as she finds out more about him instead of being repulsed by his past/background and his being an orphan she just falls in Love with him all the more.
And then she realizes that helping him continue his dysfunctional relationships is not good for either of them especially him so she breaks it off for both of their sakes. I think it is wonderful that they get back together and find the true real meaning of Love..(You have to read it as a romantic would read it and you have to read all of the books. And you have to understand that the BDSM is only a small integral part of the plot to explain how the story begins, evolves and ends.)
Anastasia is ready for love when she meets Christian and once he meets her he realizes that loving her is the most important thing and that sex is a very important integral part of LOVE and that BDSM has no place in really loving someone. (You really see the this in Fifty Shades Darker on the sail boat when he teaches her to sail it and he tells her "He Loves seeing her so happy..That's when both we/he can tell he is truly in Love with her unselfishly..)