Diesel Locomotives on Scottish Railways covers most of Scotland from Thurso in the far north to the border with England, from 1974 until the present day. The book covers diesel locomotives from Class 20s up to the most powerful Class 70s. In Scotland from the late 1950s, various prototype diesel locos were tried out with different degrees of success. Some were destined to be withdrawn very early while others have continued in service and are still going today, such as the occasional example of a Class 20 or Class 47. One of the most common early diesels in Scotland was the English Electric Class 37, which could be found working almost anywhere. A few still work in Scotland. Possibly the best of the early diesels was the Class 55 - the Deltics. They were introduced from May 1961 on the East Coast Main Line and also worked north of Edinburgh to the Central belt towards the end of their careers.

In this book, author Colin J. Howat shows a wide variety of diesel locomotives in action on Scotland's railways.