Behind the Walls of Terra

From Author Wars - https://authorwars.com/publications/behind-the-walls-of-terra-218053.html

Overview:

Title: Behind the Walls of Terra
Author: Philip José Farmer
Year: 1976
Publisher: Ace Books
Price: $1.25
Pages: 188
Binding: Paperback
Type: Novel
Title Reference: Behind the Walls of Terra
Notes:
• Later, likely second, printing of the 1970 Ace ed.
• From an ad in the back which lists verified Le Guin titles [one of which was published Dec.'75], the year can be placed as 1976
• Cover art is credited to Forbes on copyright page, cover is also signed B.Forbes