The Junipers of the World contains a synthesis of data on evolution by examining:

Geographic Variation: Pan-Arctic variation in Juniperus communis, etc.
Speciation in sections of the genus: Species concepts, Speciation in Juniperus section Juniperus, etc.

In addition, Keys to Juniperus are provided by region: Eastern Hemisphere, Europe (including Azores, Canary Islands, Asia Minor and Africa), Central Asia (Turkmenistan to western Himalayas), China, Far East (Japan, Korea, Sakhalin Island, Taiwan), Western Hemisphere, Continental North America, United States and Canada, Mexico and Guatemala, and the Caribbean.

Also included are Species' Descriptions, Distribution Maps and Plant Photos, and chapters on Hybridization, Ecology, Cultivated Junipers, Commercial uses of leaf and wood oils of Juniperus, a Cross Indexed Synonymy of Juniperus, and Tables on the Leaf essential oils by species in sections.

This book supplements the web site [...] and the reader will find literature citations and a detailed discussion of data that is not present on the web site.

"The Junipers of the World is now the authoritative reference for Juniperus"
"Prof. Adams has presented arguments for the recognition of species and varieties by showing the data analyses that led to taxonomic decisions. This is one of the few treatments that really integrates data and the reasoning behind taxonomic decisions. In addition, Prof. Adams is candid in admitting that the recognition of some taxa are not well supported and deserve additional study."

"An essential reference book that will be useful for herbaria, museums, wildlife biologists, Range scientist, foresters, ecologists and all who are involved in identification and study of Juniperus species."