He first garnered significant critical acclaim with his "The Chronicles of Prydain" series. The second volume ("The Black Cauldron") was a runner-up for the 1966 Newbery Medal; the fourth ("Taran Wanderer") was a "School Library Journal" Best Book of the Year; the fifth and concluding volume ("The High King") won the 1969 Newbery. Alexander was included in the 1972 third volume of the HW Wilson reference series, "Book of Junior Authors and Illustrators"—early in his career as a children's writer, but after "Prydain" was complete. For his contribution as a children's writer, Alexander was U.S. nominee in 1996 and again in 2008 for the biennial, international Hans Christian Andersen Award, the highest recognition available to creators of children's books. Many of Alexander's later books received awards "The Marvelous Misadventures of Sebastian" won the 1971 National Book Award in category Children's Books and in 1982 "Westmark" also won a National Book Award.