The Anthology, nine books in Greek, is the longest surviving astrological treatise from antiquity and the single richest source for how Hellenistic astrology was actually practiced rather than only theorized. Valens included more than a hundred sample nativities drawn from his own case files, complete with his working calculations, making the text an unusually direct window onto real professional method rather than an abstract exposition.
Modern reconstruction of Hellenistic technique, including the systems of Arabic Parts and Egyptian planetary terms that the atlas describes across its astrological content, draws heavily on Valens alongside Ptolemy and the fragmentary earlier sources both of them preserve. The standard critical edition is David Pingree's 1986 Teubner text; Valens has no ancient biography beyond his own book, so essentially everything known of him as a person, rather than as a technical author, is inferred from what he chose to say about his own training and travels within it. Where Ptolemy's Tetrabiblos aimed to give astrology a philosophical justification within a broader natural science, Valens made no such argument and simply assumed the discipline's validity, a difference in temperament that later historians of astrology have used to characterize the whole distinction between astrology's theoretical and its practical wings in the ancient world.