Bernard Waber, the author of such children's favorites as "The House on East 88th Street" and "Lyle, Lyle Crocodile," has died.

Waber died May 16 at his Long Island home after a long illness, publisher Houghton Mifflin Harcourt announced Monday. He was 91.

Waber's "warmth, energy, artfulness, elegance, and abiding respect for children were epitomized in his books," Houghton's senior vice president and publisher of books for young readers, Betsy Groban, said in a statement. His 33 books have sold 1.75 million copies, the publishing company said.

Waber debuted as an author in 1962 with "The House on East 88th Street," which introduced readers to the loveable Lyle, first spotted in a bathtub in an Upper East Side brownstone. Lyle's story continued in "Lyle Finds His Mother," ''Lyle and the Birthday Party" and other works. Waber also wrote many non-Lyle books, such as "Ira Sleeps Over," in which a boy fears he'll be teased for bringing a favorite stuffed teddy bear to a friend's house.

Waber was a native of Philadelphia and a graduate of what was then known as the Philadelphia College of Art.

He is survived by his brother, three children and four grandchildren. His final book, "Lyle Walks the Dog," was a 2010 collaboration with his daughter, Paulis.