The book investigates the intricate relationships between cooperative bacteria and their animal hosts. It explores how these microbial partners influence host physiology, development, immunity, and even behavior, drawing on a range of examples from across the animal kingdom. The work examines the evolutionary pressures that shape these symbiotic associations and the molecular mechanisms underlying their interactions.

This work is recognized as a comprehensive overview of host-microbe symbiosis, suitable for advanced students and researchers. Its detailed examination of the biological and evolutionary aspects of these relationships provides a solid foundation for understanding microbial influence on animal life. The book is noted for its thorough synthesis of current knowledge in the field.