Leonardo da Vinci's Annunciation is one of the most extraordinary and mysterious paintings of the 15th century. The essay revolves around one of the many questions raised by this masterpiece: the interpretative enigma concerning the open page of the sacred codex that the Virgin is reading when she is suddenly distracted by the angel's arrival. Through attentive iconographic examination, supported by a historical-artistic overview on the subject of the Annunciation, the authors reveal unknown aspects of the work linked to the Jewish tradition and Neoplatonic philosophy, providing a decisive contribution to enhancing our understanding of the genius from Vinci.