Xingu and Other Stories Book

Xingu is a short story, but there aren't a lot of novels that begin with X for my reading challenge.

This was an amusing story in 3 acts. 1st act establishes the small town ladies literary lunch society (limited in size to 6 members because of the size of one of the members dining room). They are excited to have a famous author for their upcoming lunch, and peeved at one of the members (Mrs. Roby) who doesnt bother to read the newest books because she prefers old fashioned authors like Trollope.
Act 2: lunch with the author is unpleasant because she's snooty. When she scoffs at their literary pretensions, Mrs Roby says they've been so busy studying Xingu, the author pretends she knows what this is to avoid being embarrassed. The other ladies chime in to compound her embarrassment until she leaves.
Act 3: after, the other ladies look up Xingu and discover it's the name of a river in the Amazon. They are still not sure however if Mrs Roby belongs in the lunch club, however.