For a nearly 75-year-old fantasy novel, the book begins with a remarkably modern sentence:
Dr. Reed Chalmers, Professor of Psychology at the General Hospital, worked out the theory of the simultaneous existence of an infinity of possible worlds.
Multiverses are all the rage in cosmology today but parallel worlds were a seldom-used concept either in science fiction or fantasy in 1940 when Fletcher Pratt came up with the multiple possibilities for humor and adventure inherent in sending protagonists into the world of story and myth. He teamed with L. Sprague de Camp, then just breaking into regular sales, for a series of stories they sold to John W. Campbell’s Unknown Fantasy Fiction. “The Roaring Trumpet” (May 1940) and “The Magic of Mathematics” (August 1940) were incorporated into The Incomplete Enchanter, published in 1941 by the prestigious mainstream publisher Henry Holt. Prime Press, a rival small science fiction press to Gnome, reprinted it in early 1950, a year after they published de Camp’s similarly-themed Lest Darkness Fall.
At just about the same time in 1950, Gnome published de Camp and Pratt’s The Castle of Iron, an expansion of the Unknown novella from April 1941, presumably for no better reason than confusing bibliographers. That’s because this title is the sequel to The Incomplete Enchanter and not Gnome’s earlier de Camp and Pratt book, The Carnelian Cube.
In other words, Prime printed a book that looked like a sequel to an earlier book of theirs but wasn’t and Gnome printed a book that was a sequel but not to their earlier book – with both of them hitting bookstores at the same time.
I can understand why both of them did it. Publishing books randomly because you can get the rights, though, is not a long-term business plan.
August Derleth reviewed this book in the September 27, 1950 Madison Capital Times:
[It] is a far better brand of fantasy entertainment [than Minions of the Moon].
The Castle of Iron, by L. Sprague de Camp and Fletcher Pratt, 1950, title #7, 224 pages, $2.00. 3500 copies printed.
Hardback, Red-orange boards with wine-red spine lettering and a wine-red drawing of a man riding a hippogriff on the front boards. Jacket illustration by Hannes Bok. Physically smaller than most other Gnome Press titles at 5.1×7.6 in. “FIRST EDITION” on copyright page. Printed by H. Wolff. “A Science Fantasy Adventure” on title page. Unsigned Introduction. Back cover: promotes Men Against the Stars. Gnome Press address given as New York 57.