This was the second book and first solo work of James E. Gunn, already a professor at the University of Kansas, where he would start a famed program in science fiction as literature. His first book was also published by Gnome, Star Bridge with Jack Williamson. The middle initial stands for Edwin and his earliest stories were published under the pseudonym of Edwin James. The use of the initial on his works is erratic, with no pattern that I can see. There should be no confusion within the field, however: there is no other James Gunn. Outside the field, several figures named James Gunn appear, especially an astronomer by name of James E. Gunn, with the E. standing for Edward.
Floyd C. Gale reviewed the book for the April 1956 Galaxy:
[I]t did just what it set out to do – create excitement.
This Fortress World, by James E. Gunn, 1955, title #50, 216 pages, $3.00. 4000 hardbound copies printed.
Hardback. Jacket design by Murrary Tinkelman. “First Edition” stated on copyright page. Manufactured in the U.S.A. by H. Wolff. Back cover: 43 titles. Gnome Press address given as 80 East 11th St., N.Y. 3.
1) CURREY (A) Blue-gray boards with light blue cloth shelf back, lettered in black
2) CURREY (B) Tan boards, spine lettered in black
Note: I turned the contrast up very high on my scanner to show that the earlier variant has a pattern of red rectangles inside of red rectangles. The actual boards are much darker, and so is the spine.