The author of the rhetorical treatise On Style is traditionally identified as Demetrius, though his precise identity remains uncertain. Scholarly consensus, based on internal references and stylistic analysis, places the work's composition in the Hellenistic period, likely the 2nd or 1st century BCE. The author displays extensive knowledge of prior rhetorical theory and classical Greek literature, indicating he was an educated rhetorician or critic, but no further biographical details survive.

His sole extant work is the treatise On Style, a complete manual on literary expression. It is a major surviving ancient work devoted to literary style, systematically analyzing four styles: the elevated, elegant, plain, and forceful. The treatise preserves otherwise lost Hellenistic rhetorical doctrines and provides valuable literary criticism through its extensive use of examples from classical Greek texts. Its original analysis of the forceful style, characterized by brevity and emotional intensity, and its utility as a compositional guide ensured its influence into later antiquity and the Renaissance.