If you live in the Western United States or Canada and have a garden, then you should have this book.
My copy was a gift and has a 1972 copyright, but the vast majority of the information is timeless and enduring.
One of the most interesting features of the book is how it provides fairly detailed maps which classify each location in the western US to one of 24 'Climatic Zones'. The vast majority of the detailed plant information within the book provides zone specific data.
A general knowledge portion of the book discusses topics such as: Soils and Planting Mixes, Planting Techniques, Watering, Fertilizing, Pruning, Pest and Disease Control, Planting a Lawn, and Garden Maintenance.
The majority of the book is composed on the "Western Plant Encyclopedia" which is an alphabetic listing of hundreds of plants. The listings include zone specific information on planting, pruning, watering, etc. There are a fairly large number of illustrations.
Many nurseries in the west keep copies of the Sunset Western Garden Book around as the primary reference guide. I understand that the most current edition now contains information for Alaska, Hawaii, and Western Canada.