GUANTANAMO BAY NAVY BASE, Cuba — The prison library was wrong to reject a 9/11 victim’s gift of a copy of Stephen King’s masterpiece “It,’’ and will add it to the library’s 19,000-book collection, a military spokesman said Monday.

The epic 1986 horror novel about a monster that lurks in some Maine sewers was the only one refused from a donation of about 70 brand-new books by a man whose father was killed at the World Trade Center on Sept. 11, 2001.

Library workers spent months reviewing the donated books, which included the works of William Shakespeare, Charles Dickens and Ernest Hemingway, before accepting all but “It’’ without explanation, the Miami Herald reported Sunday.

Monday, Army Capt. Andi Hahn said the library was wrong to exclude that title because “It’’ was approved for circulation as far back as 2008, and another copy was already in the detention center library. She did not know if any prisoners had read the earlier copy.

” ‘It’ is currently being bar-coded and will be put in the library,” Hahn said.

A contractor named Milton who has managed the library in recent years tells visiting reporters that he screens books and videos and sometimes excludes those with violent or sexual themes. “It” includes a sex scene between a 12-year-old girl and five boys of about the same age, one after another, which apparently didn’t bother whoever was functioning as censor in 2008.