The Hostage of Zir

From Author Wars - https://authorwars.com/publications/the-hostage-of-zir-231081.html

Overview:

Title: The Hostage of Zir
Author: L. Sprague de Camp
Year: 1977
ISBN-10: 0399120971
Publisher: Berkley/Putnam
Price: $7.95
Pages: 213
Binding: Hardcover
Type: Novel
Title Reference: The Hostage of Zir
Notes:
Cover artist is uncredited, but the cover is clearly signed in the lower right corner. Month ("7712") on front flap seen in ebay.com photo.