As stated in the subtitle, Conifers of the Temperate Zones and Adjacent Regions, the book covers not only the colder and cooler temperate zones of both hemispheres but also follows temperate genera into the subtropics and adjacent high-elevation tropics. The concept governing which taxa to include or exclude is discussed in the Distribution and Climate chapter (see the first page-pair below).
The main purpose of the book is to present an overall picture of the astonishing biodiversity among temperate conifers in their natural habitats to a wide audience as accurately and accessibly as possible. Thus the book is not a technical treatise or new botanical treatment of the subject with newly proposed name changes. As the focus is on conifers in their natural habitats, see page samples below, the main principle behind their ordering is their natural distribution; thus, they are arranged alphabetically in 11 regional chapters rather than alphabetically overall.