I was furious when that "sequel" came out for GWTW. It sickened me, the soap-operaish way Scarlett and Rhett got back together. I always imagined something quite different. IMO, Rhett at the end of the novel is just battered from years of being hurt by Scarlett's foolish infatuation over Ashley. But they belong together. Scarlett will prove to Rhett how much she loves him, and Rhett will realize that they belong together, and they'll live happily ever after
By the way, Rhett Butler is one of my favorite all-time literary characters. He's tough on the outside, but he's tender and loving on the inside, and he has a great sense of humor. I practically want to strangle Scarlett in both the book and the movie, because Rhett does everything possible at every situation to show how much he cares about her, and she's just oblivious. Scarlett! Men like that don't grow on trees!
And slightly off-topic: what do you think about the ending to Cosi fan tutte? I've never believed that in the end the original couples just get back together. I think Mozart and da Ponte deliberately made the ending ambiguous. It's clear that the "test" opened a can of worms that can't be closed again. That;s just my take.