Ephorus'
magnum opus was a set of 29 books recounting a
universal history. The whole work, edited by his son Demophilus—who added a 30th book—contained a summary description of the
Sacred Wars, along with other narratives from the days of the
Heraclids up until the taking of
Perinthus in 340 BC by
Philip of Macedon, covering a time span of more than seven hundred years. According to
Polybius, Ephorus was the first historian to ever author a universal history. For each of the 29 separate books, Ephorus wrote a
prooimion. The work was probably simply named
Historiai, and followed a thematic, rather than a strictly chronological order in its narrative. These writings are generally believed to be the main or sole source for
Diodorus Siculus' account of the history of Greece between 480 and 340 BC, which is one of only two continuous narratives of this period that survive. It is clear that Ephorus made critical use of the best authorities. His history was highly praised and read in antiquity, and later ancient historians freely drew upon his work. Large parts of the history of Diodorus Siculus may have originated in Ephorus's history.
Strabo attached much importance to Ephorus's geographical investigations, and praised him for being the first to separate the historical from the simply geographical element. In his
Geographica, Strabo quoted Ephorus at length.
Polybius, while crediting him with a knowledge of the conditions of naval warfare, ridiculed his description of the 362 BCE
Battle of Mantinea as showing ignorance of the nature of land operations. ==Additional works==