This is what Time magazine reported:
"Stein says that as mayor, Palin continued to inject religious beliefs into her policy at times. "She asked the library how she could go about banning books," he says, because some voters thought they had inappropriate language in them. "The librarian was aghast." That woman, Mary Ellen Baker, couldn't be reached for comment, but news reports from the time show that Palin had threatened to fire Baker for not giving "full support" to the mayor."
And this from Boston Herald (who uses a different last name for librarian):
"According to news coverage at the time, the librarian said she would definitely not be all right with it. A few months later, the librarian, Mary Ellen Emmons, got a letter from Palin telling her she was going to be fired. The censorship issue was not mentioned as a reason for the firing. The letter just said the new mayor felt Emmons didn’t fully support her and had to go.
Emmons had been city librarian for seven years and was well liked. After a wave of public support for her, Palin relented and let Emmons keep her job."