Watchers of the Dark

From Author Wars - https://authorwars.com/publications/watchers-of-the-dark-123661.html

Overview:

Title: Watchers of the Dark
Author: Lloyd Biggle, Jr.
Year: 1969
Publisher: Curtis Books
Price: $0.75
Pages: 176
Binding: Paperback
Type: Novel
Title Reference: Watchers of the Dark
Notes:
- © 1966 No other date, printing or number line
- Date taken from Dennis Lien's Curtis Books checklist in The Science Fiction Collector #14 (1981).
- The artist is not credited, no visible signature on the artwork; cover art is identical with #71 of the German Perry Rhodan series: http://www.perrypedia.proc.org/wiki/Quelle:PR71