Hi Doug,
The 1949 edition of this book was reprinted by Railhead Publications. The original was essentially a promotional booklet during the time that the "Narrow Gauge Fever" was spreading throughout the U.S. and expounds upon the value of (early) narrow gauge railroads, mentioning specific contemporary examples and their experiences to date. This 3rd printing contains an expanded Directory of Narrow Gauge Railways, that is reasonably accurate and reprints several contemporary manufacturers advertisements.
I have a copy of the third printing (paperback and inexpensive) and the book is a good companion to Hilton's tome on the same subject. You might be about to still get copies from Railhead.
The ISBN is 0-938936-02-6.
Best Regards,
Glenn