"The Traveling Engineers' Association to Improve the Locomotive Engine Service of American Railroads: Examination Questions and Answers for Firemen for Promotion and New Men for Employment" by the Traveling Engineers' Association may be a niche book to some, but it's an invaluable text. The railway system is often under-appreciated in the United States since it's not commonly used for traveling purposes. This book helps bring light to some of the important and groundbreaking engineering that has gone into locomotives.