This 1958 booklet finishes the series of along-the-way guides for each of SP’s “four great routes.” SP published an along-the-way guide for the Coast Daylight route, but it was in a very different format as can be seen in this post from 2012.
Since the Sunset and Golden State routes were identical west of El Paso, much of this guide necessarily replicates the Golden State guide. Perhaps because there was extra room, this guide also dedicates most of a page to drawings and descriptions of six different desert plants, including the yucca, ocotillo, cholla, prickly pear, barrel cactus, and saguaro (which the guide spells sahuaro).
This guide and the Shasta guide are the only ones that credit the artist who did the maps: Clyde Magill, who the guides say was a “western artist.” According to AskArt, Magill was born in Texas in 1904 and spent most of his life in California where, among other things, he supposedly was art director of Newsweek magazine for 50 years (unlikely because he died in 1969 at age 65, so he would have had to have started as art director at age 15). In 1942, he did a one-man show at the San Francisco Museum of Modern Art. A sample of his art work can be seen here.