In the Still of the Night — Jill Churchill

Lily Brewster and her brother Robert have all the appearances of being filthy rich, even though the family fortune went out the window with the crash of 1929. But thanks to great-uncle Horatio, who left them Grace and Favor Cottage, a huge mansion on the Hudson not far from Franklin Roosevelt's Hyde Park, the Brewsters live in the style to which they had become accustomed -- with a few troublesome limitations.

To make sure Lily and Robert didn't go back to being society bums, crafty old Horatio attached some strings to his bequest -- and a penny-pinching attorney to manage the funds. Now the poor Brewsters have to actually work for money to survive, and Lily comes up with a brilliant scheme. They can turn a profit while they hobnob with their society friends, luring them to Grace and Favor for a paying weekend with the promise of big-name celebrities as guests.

If Sinclair Lewis hadn't been working on a new book, he might have joined the party; if Amelia Earhart hadn't been busy planning her cross-Atlantic flight, history might not have its own unsolved mystery. And if the Brewsters' celebrity/society bash hadn't been short on luminaries and long on snide barbs and open hostility among the guests, the glittering, glamorous affair might not have turned into a whodunit with one guest dead, one missing, and Lily and Robert chasing a murderer who is ready to strike again.