[1] The principal work was intended to cover human history from the beginning until the time of the Caesars, focused on Greece and her rulers, nations and peoples, and it was from this base that Justin created his Epitome, slimming it down by focusing on "whatever [parts] was most worthy of being known" and removing parts which "were neither attractive for the pleasure of reading, nor necessary by way of example",[4] resulting in a work approximately one-sixth the length of the original[5] and described as a "capricious anthology" rather than a regular epitome.

It is believed to have been written in Rome due to a section in the preface where Justin writes that he had composed the work "during the leisure that I enjoyed in the city".

Some scholars instead date the work to the 4th century, based on linguistic analysis, and argue that partially obsolete information might not have deterred a non-historian from writing an epitome.

Analysis of the Epitome has led scholars to see a connection, through the similarity of metre and content within selected sections, between the work of Justin and that of the earlier Tacitus.

In particular, it provides important insights into his father, and the namesake of the work, Philip II, with Justin being one of just two surviving narrative sources, alongside the earlier Diodorus.

[10] This interpretation is disputed by most historians, and instead this is likely to be a transference of the themes of Trogus, where immoderation was seen as an unfit attribute, and a direct cause of the loss of imperium.