A batch of the wonderful Dell "Map Back" books. First published in 1943, they ran numbers 1 through about #550, when the maps were no longer featured on the backs. Numbers 1-5 were also map-less, although a later printing of #4 ("The American Gun Mystery") did have a map.
Number 55, The DA's Daughter by Herman Peterson.
Number 111, Greenmask by Jefferson Farjeon. Joseph Jefferson Farjeon (June 4, 1883--June 6, 1955) was a decendent of Thomas Jefferson. A prolific author of mysteries, he wrote over 80 novels.
Number 135, Meat for Murder by Lange Lewis.