Overruled

I'm among the minority, I didn't like the book. But I guess we all have different cup of coffee, don't we? I'm a sore loser, that's why I hate love triangle. I usually end up with team “guy/girl who the female protagonist didn't chose”.
So long story short it's about the guy impregnated his high school girlfriend, when they were both 17. The guy still leave Missisippi because the girlfriend told him so to fulfil his dreams & give their child the better future, or they thought so. The guy lives in a big city & the girl stays in their little town. They agreed for the open relationship, worked for 10 years.
Suddenly the bomb is dropped, the guy received the invitation of the girl's wedding. And the stupid things ever (imho) the boy asked the girl who he's currently sleeping (& secretly falling for him) with, to win again his highschool girlfriend & the mother of his daughter.
Okay, there goes my interest, it left the building.
For me, there's something about the past that sentimentil, maybe its nostalgic feeling or the memories, I don't know. I know times make some love fades, but in this story I don't want that love fade. I want the guy back with his high school girlfriend, not just because they had a a daughter together, but also the nature of their relationship, it's different with “friend with benefit” with his current “girlfriend”.
I'm not happy with the ending. But I still appreciate how the guy said goodbye to his young love, it was still sweet.