A challenged book, by the way, is one that someone or some group has tried to have removed from a public or school library for whatever reason. These days, the problem with Huck Finn is racial, but in the beginning when this book was published in 1884, it was the general tone and the behavior of the main characters that ruffled the feathers of the prudish.
The committee members of the library in Concord, Massachusetts said these things right before banning it:
It was "couched in the language of a rough, ignorant dialect"
"All through its pages there is a systematic use of bad grammar and an employment of inelegant expressions."
"It deals with a series of experiences that are certainly not elevating."
In 1905, a letter exchange went on between the head librarian at Brooklyn College and Mark Twain. The librarian wrote to Twain to tell him about the children's department librarian of the Brooklyn Public Library who was highly disturbed by Huckleberry Finn and Tom Sawyer. She wanted them removed from her shelves because the boys demonstrated "coarseness, deceitfulness and mischievous practices." They were just not good role models for children.
As only Mark Twain could have done, here is his response:
21 5th Avenue
Nov. 21, '05.
I am greatly troubled by what you say. I wrote Tom Sawyer & Huck Finn for adults exclusively, & it always distressed me when I find that boys and girls have been allowed access to them. The mind that becomes soiled in youth can never again be washed clean. I know this by my own experience, & to this day I cherish an unappeased bitterness against the unfaithful guardians of my young life, who not only permitted but compelled me to read an unexpurgated Bible through before I was 15 years old. None can do that and ever draw a clean sweet breath again on this side of the grave. Ask that young lady - she will tell you so.
Most honestly do I wish I could say a softening word or two in defence of Huck's character, since you wish it, but really in my opinion it is no better than God's (in the Ahab & 97 others), & the rest of the sacred brotherhood.
If there is an Unexpurgated [Bible] in the Children's Department, won't you please help that young woman remove Tom & Huck from that questionable companionship?
S. L. Clemens
Ahhhhhhh, that makes me giggle every time I read it. The children's department librarian was incensed, and she removed the books from her department and moved them to the adult section of the library. Eventually word got out about the dispute, and rumor spread that the two books were banned from the children's library.
Newspapers rallied and called the librarian a "literary prude." Eventually the problem died down but only for that particular library. Huckleberry Finn has had champions and enemies from its first day off press. I lost track of counting the editions on amazon.com somewhere in the mid fifties, but the list seemed to go on forever. Almost 125 years after it was written, the book is still a hit.