It is thanks in part to Livy that we have a clearer vision of the Romans than we do of many other ancient peoples. Livy, who lived during the span of Roman history when Julius Caesar was assassinated and Augustus came to power, wrote 142 books about the history of Rome from its founding (Ab Urbe Condita).
About the coming book discussion of Livy
Livy
The Structure of Livy's Ab Urbe Condita