I can also recommend: "The Earth: An Intimate History" by Richard Fortey
replySecond for John McPhee! Also Rising From the Plains.
replyReferences to his books should carry a warning - something to the effect of:
reply"may inspire circuitous road trips involving many stops dangerously examining road-cuts on busy interstate highways"
I would pay good money for a field guide/itinerary to accompany "Assembling California".
replyMore directly related to the Green River, I found Wayne Ranney's "Carving Grand Canyon: Evidence, Theories, and Mystery" an accessible/engaging intro to deep geological mysteries.