At first glance It Must Be looks like a self-indulgent diary. One of those "vanity press" books when one wants to see themselves in print. In reality It Must Be is an unflinching look at our greatest natural resource, water. Specifically, the Colorado River. Hidden in the journal of a winter adventure down the Grand Canyon Barnes plays devil's advocate and dares to ask about man's wanton waste while recognizing we need water for work and for play beyond sustenance. It Must Be speaks to the naturalist, the avid boater, the ecologist, and the historian, but his most obvious audience is the artist. Brilliant color and detail explode from nearly every page. Canyon walls come alive in shades of red and blue, black and green, while the river's ever-changing energy is captured in the same. While It Must Be is short and sweet (46 pages cover to cover) its final message is loud and clear, "how much do you need?" ( )