This unique full-color field guide is essential not only for the visitors to any of the 38 sites covered but also for anyone who seeks to understand why shamans in the Far West created rock art and what they sought to depict. As one of North America's foremost authorities on prehistoric art, Whitley is on the cutting edge of dating and interpreting the images as well as describing the cultures that created them.
As a guide, David Whitley's book remains very useful, though conditions at the sites have surely change in the almost 30 years since its publication. Its maps will get you to the sites, and the brief descriptions and many photos will help you understand what you are looking at. Whitley also is a strong proponent of intelligent tourism and preservation of the thousands of examples of rock art scattered across Southern California and Nevada.
But there's a caveat. Whitley has been probably the strongest advocate in North America of the theory that Native America rock art represents the trance visions of shamans. He lays out his views at pp. 14-25, writes briefly about possible relation of some art to puberty rituals at pp. 25-28, and strongly rejects all other interpretations at pp. 28-33. Today few anthropologists accept the shaman vision explanation of rock art (though I review elsewhere a book from 2017 that embraces it enthusiastically). As far as I know, Whitley continues to propound this idea. So my advice is use the book as a guide, but take the analysis with a grain of salt.