The Handbook of New Zealand Mammals is the only definitive reference on all the land-breeding mammals recorded in the New Zealand region (including the New Zealand sector of Antarctica). It lists 65 species, including native and exotic, wild and feral, living and extinct, residents, vagrants and failed introductions. It describes their history, biology and ecology, and brings together comprehensive and detailed information gathered from widely scattered or previously unpublished sources.

The description of each species is arranged under standardised headings for easy reference. Because the only native land-breeding mammals in New Zealand are bats and seals, the great majority of the modern mammal fauna comprises introduced species, whose arrival has had profound effects both for themselves and for the native fauna and flora. The book details changes in numbers and distribution for the native species, and for the arrivals it summarises changes in habitat, diet, numbers and size in comparison with their ancestral stocks, and some of the problems they present to resource managers.

For this third edition, the text and references have been completely updated and reorganised into Family chapters. The colour section includes 14 pages of artwork showing all the species described and their main variations, plus two pages of maps.