As a full-time creative director at Dover Books, Paul illustrated countless coloring books, but as a freelancer, he illustrated more than 34 children’s books for publishers such as A. Knopf, MacMillan, Little, Brown, Dial, Nelson, and Dutton; and writers such as Walter da la Mare, Mary Ellen Chase, and Anne Sinclair Mehdevi. Otto the Grumpy Boy was a collaboration with his wife, Emily, who wrote it. He won 1966 Printing Industries for America award for The Persian Folk Tales, and is listed in Illustrators of Children’s Books: 1957-1966.