Rights of trains is a good book even though I don't know any RR's left operating with train orders. Nowadays with radio everywhere Track Warrants (or something similar) are the way to go.
Operating rules for Train Orders was the hardest part of the Conductor's exam. Since Track Warrants were introduced they have been continually simplified as crews were still not always paying attention to what they said. For example meet orders have been dropped. Now a dispatcher will only give you a warrant to a meet point and not issue the next warrant until the meet is assured. Most accidents that occur today are when someone overruns their limits.