The two sans under the title are Standard Medium and Standard Medium Condensed.
I included the title page because it’s a double-page spread, and the book designers were also given credit: “Designed by The Etheredges”.
Pretty good for a $1.50 paperback! The original edition was printed in 1940, also by Harper & Row.
Contributed by Nick Sherman
Contributed by Ivar Sakk
Contributed by Blythwood
Contributed by Estereográfica Editorial
Contributed by Florian Hardwig