Harold M. Sherman was a psychic researcher who was famed for his ESP experiments. When he wasn’t trying to prove the existence of ESP, he was a writer who wrote in several different genres. The Green Man is a satire about what happens when an alien lands on Earth in 1947 and interrupts a Notre Dame football game. The Green Man was first published in 1946 and it’s been reprinted several times. Sherman even wrote a sequel called The Green Man Returns.
The identity of the cover artist is unknown.