This volume serves as a comprehensive reference guide designed to categorize and explain the biological diversity of the animal kingdom for a general audience. The author, Kenneth P. Bailey, utilizes the structured framework of the Collins Wide World Encyclopedia series to present taxonomic information, habitat descriptions, and behavioral characteristics of various species. The text functions as an educational resource, synthesizing scientific classification with accessible descriptions to provide a foundational understanding of global fauna.

The subject matter points to a standard, mid-twentieth-century educational reference text intended for students and general readers seeking a broad overview of zoological science. Its framing suggests a structured, descriptive approach to biology that prioritizes clarity and breadth of coverage over specialized research or niche analysis.