Well, the 'Murder on the Orient Express' has elements that are drawn from a true story. Christie used the general idea of a high - profile crime as a starting point. But in the book, she added her own fictional characters, motives, and the intricate plot twists that we all love. So it's not a completely accurate retelling of a true story but has its roots in real - life events.
One similarity is the general concept of a major crime as the starting point. Just as in real - life high - profile crimes, the book also has a serious crime at its core.