What a beautifully written book. McCullers writes with this undertow of gentle sadness that feels embodied in lived experience. I find there is almost a warmth to the sadness conveyed by the narrator's voice (contrasted with the coldness and brutality of a Houellebecq, for example).
I think the book perfectly describes what it's like to be stuck in loneliness. The feeling of being trapped and unable to will yourself out of a choking reality. The protagonist, 12 year old Frankie Adams invents a delusion, a fantastical world in which her life will suddenly change after The Wedding. This is the internal refuge she creates to tolerate the stagnant monotony of life around a grimey kitchen table with her nanny Berenice and younger cousin John Henry.
While Frankie harbours this childlike delusion of change, Berenice is the sober eyed realist who will absolutely not humour this foolishness one bit. One evening, the stalemate is broken. There is a discussion about the impossibility of being someone else and feeling "caught" by life. Being trapped by life's circumstances and being unable to change it. And this feeling of "looseness", of being unable to connect with others you see in front of you. It's an exquisitely tender scene where these very different characters seem to finally understand each other.
The ending supposedly ends on a happy, hopeful note. But I interpret it as a harbinger of future devastation and inevitable disappointment that can only come from being so in love with one person.

Lovely review. I agree with the bit about the ending. It feels like the book never really leaves that interminable setting.