Kelley has written and illustrated many children's books from the 1970s onward. For the Who Was biography series, she illustrated the lives of Leonardo da Vinci and King Tut, wrote and illustrated Pablo Picasso, and wrote biographies of Abigail Adams, Roald Dahl, and Dolly Parton. She wrote and illustrated The Dog Who Saved Santa and illustrated many entries in the "Let's Read and Find Out" science series.