The work is an anthology of nearly 200 “hieroglyphics,” or allegorical emblems, said to have been used by the Pharaonic scribes in describing natural and moral aspects of the world. Translated into Greek in 1505, it informed much of Western iconography from the 16th through the 19th centuries. 
The text of the Hieroglyphica consists of two books, containing a total of 189 explanations of Egyptian hieroglyphs. The books profess to be a translation from an Egyptian original into Greek by a certain Philippus, of whom nothing is known. The inferior Greek of the translation, and the character of the additions in the second book point to its being of late date; some have even assigned it to the 15th century.[1] The text was discovered in 1419 on the island of Andros, and was taken to Florence by Cristoforo Buondelmonti (it is today kept at the Biblioteca Laurenziana, Plut. 69,27). By the end of the 15th century, the text became immensely popular among humanists and was translated into Latin by Giorgio Valla (in ms. Vat. lat. 3898). The first printed edition of the text appeared in 1505 (published by Manuzio), and was translated into Latin in 1517 by Filippo Fasanini, initiating a long sequence of editions and translations. From the 18th century, the book's authenticity was called into question, but modern Egyptology regards at least the first book as based on real knowledge of hieroglyphs, although confused, and with baroque symbolism and theological speculation, and the book may well originate with the latest remnants of the Egyptian priesthood of the 5th century.

Though a very large proportion of the statements seem absurd and cannot be accounted for by anything known in the latest and most fanciful usage, there is ample evidence in both books, in individual cases, that the tradition of the values of the hieroglyphic signs was not yet extinct in the days of their author.

This approach of symbolic speculation about hieroglyphs (many of which were originally simple syllabic signs) was popular during Hellenism, whence the early Humanists, down to Athanasius Kircher, inherited the preconception of the hieroglyphs as a magical, symbolic, ideographic script. In 1556, the Italian humanist Pierio Valeriano Bolzani published a vast Hieroglyphica at Michael Isengrin's printing press in Basle, which was originally planned as an exegesis of Horapollo's. It was dedicated to Cosimo I de' Medici.

The second part of book II treats animal symbolism and allegory, essentially derived from Aristotle, Aelian, Pliny and Artemidorus, and is probably an addition by the Greek translator.