Adaptive coloration in animals. With an introduction by Julian S. Huxley.

Published during WWII, Cott's book was the first major work on camouflage in zoology, appreciated by zoologists for its scientific information and carried by many allied soldiers during the war for survival purposes. The Wikipedia analysis of this book is especially valuable. Digital facsimile of the 1957 slightly corrected reprint from the Internet Archive at this link.