For a long time I read the Iron Horse News sent out by the Colorado Railroad Museum. It was chock full of interesting goings-on related to railroads in Colorado, particularly the narrow gauge lines. A few years back I purchased Colorado Rail Annual No. 21: Robert W. Richardson's Narrow Gauge News. The book contains all of the newsletters of the original publications (then called Narrow Gauge News) from 1949-1958 as Richardson races to chronicle, preserve, and save the fast-dying narrow gauges lines.
I knew it would be dominated by D&RGW and Rio Grande Southern info, and it is, as these lines were in their death throes then (If you love those lines, you will love this book). But for the C&S fan, I didn't see much (understandably, since the C&S narrow gauge was already gone), so I never really did much other than scan a few pages here and there.
Finally, I started combing the book for DSP&P/C&S details more thoroughly and began underlining them. While they are few, there are some terrific gems among them, especially as we see some of the early signs of C&S and South Park preservation efforts.