Just bubbling this back up again. To summarize, these are the current unrecorded works by Buck that should be available to folks in the US to record (China Sky did have its copyright renewed and isn't PD):
The Long Love (1949) [written under pseudonym John Sedges]
Potrait of a marriage - For Edward Haslatt there was no thought of another woman. He loved his wife with a devotion that began with their courtship and grew with the years. Yet Margaret Haslatt had a rival more dangerous than any sloe-eyed mistress. - Edward had built his father's printing shop into a thriving publishing house. He gave himself to it with all his time and energy. But for a married man there are other demands. There is a constant conflict between his wife's needs and the pressures of his work, between his temperament and hers. There are the conflicts that simmer under the surface of every male and female, conflicts that sometimes flare into a blaze of anger
https://babel.hathitrust.org/cgi/pt?id=uc1.b4097124
Christmas Miniature (1956)
This adorable book is the story of a little boy named Sandy who can't wait for Santa Claus to visit his home on Christmas Eve.
https://babel.hathitrust.org/cgi/pt?id=uc1.b4594037
How It Happens: Talk About the German People, 1918-1933 (1947)
The book explores the events leading up to the rise of the Nazi party in Germany, from the country's defeat in World War I to the economic struggles of the Weimar Republic. Buck provides an in-depth analysis of the social, political, and economic factors that contributed to the rise of Hitler and the Nazi party. She also examines the role of the German people in this process, and how they responded to the changing political landscape. Buck draws on her own experiences living in China and Japan, as well as her extensive research, to provide a unique perspective on this pivotal moment in history.
https://babel.hathitrust.org/cgi/pt?id=inu.32000005037108
Can the Church Lead? (1942)
An essay on the place of the Church in modern society.
https://babel.hathitrust.org/cgi/pt?id=nnc2.ark:/13960/t98702g7n
Wikipedia