For people interested in the subject generally I highly recommend John McPhee's anthology "Annals of the Former World." Actually I highly recommend everything John McPhee has written but this is a good start :).
I just finished Annals of the Former World. It's essentially a 700 page-long ode to geology, using scientific terms for their prosody as much as their meaning. I once saw someone else remark that "Rising from the Plains" was the greatest western ever written.
I used to think geology was a dumb science, but this book single-handedly made me obsessed with the topic. Geology is really more like "earth history" and it's a startlingly young field, a dynamic which plays out across the volumes.
I would pay good money for a field guide/itinerary to accompany "Assembling California".
More 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.
I used to think geology was a dumb science, but this book single-handedly made me obsessed with the topic. Geology is really more like "earth history" and it's a startlingly young field, a dynamic which plays out across the volumes.