And Tango Makes Three is a childrens picture book published in 2005 about a family of penguins with two fathers.

It is the most challenged book in public schools and libraries for the second year in a row, according to the American Libraries Association.

The ALA defines a "challenge" as a "formal, written complaint filed with a library or school requesting that materials be removed because of content or appropriateness."

"The complaints are that young children will believe that homosexuality is a lifestyle that is acceptable. The people complaining, of course, don't agree with that," Judith Krug, director of the ALA's Office for Intellectual Freedom, told AP.

Other books hitting the Top Ten complained about include Maya Angelou's memoir I Know Why the Caged Bird Sings, in which Angelou writes of being raped as a child; Mark Twain's The Adventures of Huckleberry Finn, long attacked for racism; and Philip Pullman's The Golden Compass, which is widely perceived to be pro-atheism.

Macquarie National News