River Master by Cecil Kuhne is a re-telling of the 1869 Powell Expedition down the Green and Colorado Rivers. The book "humanizes" the Major, focusing on his flaws in leadership during the expedition.
Kuhne writes that Powell's book on the expedition is not a day-by-day account of the journey and is, in fact, somewhat of a fabrication combining events from his second expedition (1871-72) with the first, moving events around chronologically and geographically, and taking dramatic license with the material. He also describes that Powell glossed over or ignored his animosity with the crew.
Kuhne quotes liberally from previous biographers, most notably Wallace Stegner ("Beyond the Hundreth Meridian" and David Worster ("A River Running West"). He also quotes a great deal and is heavily influenced by Stanton's "Colorado River Controversies" - Stanton was the first (I think) to point out the literary license taken by Powell in his expedition book. Kuhne also rehashes the James White controversy - White claimed to have been the first through the Grand Canyon in 1867, two years before the Powell's Colorado River Exploring Expedition.
I think that a reader that is unfamiliar with Stanton's work could benefit from reading this book. I did not learn anything new from this book because I have read dozens of books about the Powell expedition and Powell himself. If one is looking for a very complete telling of the expedition (noting the flawed leadership of Powell), I found "Down the Great Unknown" by Edward Dolnick to be a much better read that equitably deals with the dynamics between the crew and Powell.
One of the things I found greatly distracting was the errors in geography and geology in the book. For instance, he gives a mileage of 35 miles from Swallow Canyon through Browns Park to Lodore on the Green River; it's actually around 20 miles - I know...I've kayaked it. He also misidentifies the rock units in Cataract Canyon (Navajo instead of Wingate), places the Crossing of the Fathers as "near Lake Powell" rather than beneath it, and places Vasey's Paradise downstream of Redwall Cavern. This is a little nitpicky, but it distracts from the book. If he is wrong about what I do know...how much is he wrong about what I don't?
I can't really recommend this book because, in my opinion, it does not add anything new to our knowledge about the expedition and contains numerous errors.
In addition to Dolnick's book, I would recommend that readers consult the source material for this book - notably Stanton's "Colorado River Controversies". Other good reads for the source material is the 1947 collection of original documents from both expeditions from the Utah Historical Quarterly (University of Utah Press) and a nice side-by-side comparison of the Major's actual diary, his written account from his book, and the surviving diaries of the other members of the expedition "The Great Unknown" by John Cooley.