When following a road book while traveling, you need to be able to track the distance since the last road book item and the total distance. You can do this with the odometer of a car, but in practice, this is a really cumbersome method. Spark Overland has created an app for this: TripComputer!
TripComputer will be available soon, as it is currently undergoing the certification process of the app store. TripComputer will be available on Microsoft Windows 10 Mobile first, with iOS and Android to follow in the future. TripComputer comes in two versions: Free and Pro. The Free version has the basic functions for following a road book, the Pro version has many improvements and functions that make your life following a road book even more easy!
Please have a look at TripComputer and see if it might be of use for you. You are welcome to give feedback on the app.