The "essence of the American desert," as the subtitle of Craig Childs' book has it, is water. A desert, by definition, lacks it, but when water does come, it comes in torrential, sometimes devastating abundance. Childs, a thirtysomething desert rat with a vast knowledge of the Southwest's remote corners, knows this fact well. "Most rain falling anywhere but the desert comes slow enough that it is swallowed by the soil without comment," he observes. "Desert rains, powerful and sporadic, tend to hit the ground, gather into floods, and are gone before the water can sink five inches into the ground." The travels that Childs recounts in this vivid narrative take him from places sometimes parched, sometimes swimming, from the depths of the Grand Canyon to the dry limestone tanks of the lava-strewn Sonoran Desert. As he travels, Childs gives a close reading of the desert landscape ("the moral," he writes at one point, "is that if you know the land and its maps, you might live"), observing the rocks, plants, animals, and people that call it home. Some of his adventures will remind readers of Edward Abbey's Desert Solitaire—save that Childs writes without Abbey's bluster, and with a measured lyricism that well suits the achingly lovely back canyons and cactus forests of the Southwest. By turns travelogue, ecological treatise, and meditative essay, Childs' book will speak to anyone who has spent time under desert skies, wondering when the next drop of rain might fall.