The Castle of Iron is the title of a fantasy novel by American science fiction and fantasy authors L. Sprague de Camp and Fletcher Pratt, and to the novel into which it was later expanded by the same authors. It was the third story (and afterwards the second volume) in their Harold Shea series. As a 35,000 word novella it was first published in the fantasy magazine Unknown for April, 1941. The revised and expanded novel version was first published in hardcover by Gnome Press in 1950, and in paperback by Pyramid Books in 1962. The book has been reprinted by a number of other publishers since its first appearance. An E-book edition was published by Gollancz's SF Gateway imprint on September 29, 2011 as part of a general release of de Camp's works in electronic form. The novel has been combin