Where the Wild Things Are by Maurice Sendak
This is one of my favorite children’s books. For anyone who hasn’t read it, the main character, Max, throws a temper tantrum then goes on an imaginative journey when he's sent to his room. It’s not the kind of thing kids did in storybooks in the 1960's and must have made readers anxious because the book faced opposition both before and after its publication. Thanks to widespread popularity among young readers, the book won a Caldecott Medal in 1964 and in 2012 was voted the #1 Picture Book by School Library Journal. It’s sold more than 19 million copies worldwide.
Green Eggs and Ham by Dr. Seuss
Yes, that Dr. Seuss book. The clever story of Sam I Am has been banned in both the United States and the People’s Republic of China. Yertle the Turtle and The Lorax have faced opposition as well.
It's interesting that these popular books have been controversial.