For some it is the heartwarming tale of two male penguins raising a chick together, but children's book "And Tango Makes Three" is also one of the most controversial texts in America, librarians say.
The illustrated book, which is intended to teach young children about gay parents, tops the 2009 list of "most challenged titles" that the American Library Association (ALA) compiles as part of its annual "Banned Books Week."
Individuals and groups in at least 15 US states have challenged libraries over "And Tango Makes Three," seeking to have the book labeled with a content warning, moved to a different section of the library or removed from shelves altogether, according to the ALA's Office of Intellectual Freedom.
For Deborah Caldwell Stone, the office's acting director, challenges to "And Tango Makes Three" and other books illustrate the importance of Banned Book Week, which will be celebrated September 26-October 3 this year.
The event was first organized in 1982 to highlight the fact "that challenges and banning are still taking place in this country on a regular basis, that books are removed from libraries because a person disagrees with the content," Caldwell Stone said.
"We estimate that we only hear about 25 percent of the challenges," she added. "A parent comes in, complains, the book is removed from the library and we never hear about it and nobody reports it to us."
Of those challenges that are reported, Caldwell Stone says objections are increasingly "to either content that deals with gay themes, or sex."
On this year's ALA list of books is the "Gossip Girl" series, which has been described as "Sex and the City for the younger set" and "The Perks of Being a Wallflower," which the group Parents Against Bad Books in Schools lists as containing references to suicide, illegal drug use, teen sex and bestiality.
Dan Kleinman, who runs the website safelibraries.org, says his concerns are with the sort of sexual content found in "Gossip Girls."
"It is wrong to say that children should not have books because the Earth is not older than 6000 years. It is wrong to say children should not have books because there's witchcraft in them. This is silly," he told AFP, referring to some of the arguments put forward by religious fundamentalists.
But, he says, "some books have explicit, very detailed sexual conduct that is not of a teaching nature... it's just inappropriate for children."
Kleinman, whose website is a clearing house for information about challenging books, insists that he does not want to see books banned, but says there is a legitimate legal basis for restricting children's access to sexually explicit material in libraries.
"All I'm seeking is application of existing law," he said, drawing a parallel between explicit websites or films and literature.
Kleinman accuses the ALA of hyperbole in celebrating Banned Books Week. "The whole purpose of Banned Books Week is to provide this kind of misinformation," he said. "The ALA misleads people into thinking that if you keep an inappropriate book from a child that is considered censorship. It is not."
But Caldwell Stone cautions that one parent should not be able to limit other children's reading material.
"When you challenge a book and argue that it shouldn't be on the shelf at all, or that there should be restricted access to the book... then what you're saying is that my values, my morals, should dictate what other people's children are reading."
Cynthia Garcia Coll, a professor of education, psychology and pediatrics at Brown University advocates a combination of community standards and educational science to determine what is appropriate reading material for children.
"Education, when it comes to kids, is not only a matter of values -- it is partly a matter of values -- but we also have some scientific data that tells you what is good for kids and what is not and we need to pay attention to that."
Lewis Lipsitt, the founder of Brown University's Child Study Center and a professor emeritus of psychology, medical science and human development, acknowledges that some literary content can scare or upset children.
But he warns that parents should not excessively restrict the access of their children and others to challenging material.
"There's no good evidence at all, after all of these years, that the kind of things that children read are going to have a deleterious effect on them."
"Rather, what happens is that they learn about behavior of great diversity," he said.