I've read it. It's entertaining, and a lot of what goes on is based on fact, but a few things are stretched in the name of artistic license.
Weldon Hill was the pseudonym of William Ralph Scott who was from Skedee, OK, where there was in fact a "virgin" coal chute (see Evan Werkema's site at
http://atsf.railfan.net/chutes/)
This was on Santa Fe's Cushing District which ran through oil country, so steam locomotives were oil-fired fairly early on.
There was also a doodlebug on this line in the early 1950s which ran as trains #51 and 52 daily from Arkansas City to Shawnee and back, on a roughly parallel schedule to the one described in the book.
The locomotives that George maintains are described as Baldwin 4-6-0s built in 1938. I don't believe Santa Fe had any "modern" 4-6-0s; a pair of older Prairies would have been more likely in the service and region described. Of course, the railroad in the book isn't the Santa Fe, it's the "Kaw & Washita," and is likely an amalgam of the Santa Fe, Frisco and Katy, the lines Scott would have most likely been familiar with in his formative years.
I've never seen the movie they made from the book with James Garner in the title role, but I'd like to.
Scott/Hill's "Onionhead" and "The Iceman" are also entertaining, even though they contain no railroad themes.
msw