The Rocky Mountains, as defined in the book, range from northern-central British Columbia, south through southwestern Alberta, extreme northeastern Washington, northern and south-central Idaho, western Montana, western and central Wyoming, northeastern Utah, most of western Colorado, and north-central New Mexico.  The book will therefore be of most use if you wish to identify plants in those areas; but as many species included are not restricted to the Rockies, it will be useful in similar habitats outside the coverage, up to hundreds of miles away.

Plants are arranged in the book first by flower color, then alphabetically by scientific name of the family, then alphabetically by genus and species within the family/color group.  This results in similar species being placed close to each other for easier comparison.  Most of the plants each get a half a page, with about a third of that half page section devoted to the photo, the remainder to text description and a small range map.

The latter indicates the states and provinces within the Rockies the plant is found; the map is not concerned with distribution outside this area.  For example, I know that some of the species in the book are also found in California and Arizona, but the range maps never indicate that, because California and Arizona are not Rocky Mountain states.