Here are some recommendations for reference books we’ve found useful in researching these simulations; you may find them useful background reading. Some are specific to a particular simulation, while others are of more general interest.
British Railways Pre-grouping Atlas and Gazetteer - very useful in finding obscure stations and yards, and in understanding the railway geography of complex areas.
Operation Torbay - a comprehensive survey of operations on the Torbay line, it was this book that inspired us to produce our Torbay simulation.