Athenaeus was a classical Greek author who lived in Naucratis, Egypt,  around 200 AD.  Thus, he's also referred to as "Athenaeus of Naucratis."
Though we don't know much about his life, Athenaeus left behind his books. We know at least one book was lost, a history book called "On the Kings of Syria."
Athenaeus however, is best known in the food world for his book the "Deipnosophistae" (or "π" in Greek), and was probably written after 228 AD.
There were 15 chapters altogether; 10 have come down to us intact, 5 we just have summaries of.
The book is a collection of anecdotes written in dialogue form that relates the table-chatter from at least three separate banquets given by a man named Laurentius at his home in Rome. The guests around the table (in the Greek fashion) were all men -- though women were present in the room. All of the guests were of the leisured, learned Roman class -- and the talk spanned a wide variety of subjects, including food, recipes, diet, health, famous fat people, sex, condiments, gravies, and pilafs. From chapter 8 (referred to now as Book VIII), we even learn the prices in Spain at the time of barley, wheat, wine, kid goats, hares, lambs, pigs, sheep, calves and figs.
We also hear about two other food books that were known at the time -- one on breadmaking by Chrysippus of Tyana, and one on salted fish by Euthydemus of Athens. Sadly both books are lost to history. In fact, there are many Greek writers whose work was lost altogether, and it's only thanks to Athenaeus's chatty characters quoting them that we even have fragments of what they said. He also quotes a complete recipe from the Greek cook Mithaecus, the rest of whose cookbook has also been lost.
The book was first published in print in 1514 in Venice, with further printings in 1535 and in 1597.
You can download from Google Books a PDF version of the book. 
 Naucratis was between Memphis and Alexandria at the mouth of the western branch of the Nile River. Initially settled by Ionian Greeks in the 7th century BC, it had remained a prosperous Greek trading settlement, given special rights to be there by the Pharaoh. People from different parts of Greece even had their own neighbourhoods within the city. The city had temples to both Egyptian and Greek gods: Pharaoh Ahmose II even contributed toward the building of a Greek temple to maintain good relations with the Greek traders. Naucratis would have been a provincial backwater at the time of Athenaeus, far from any political power struggles, though the town had never been a political one. Its decline had begun after 300 BC and the founding of Alexandria, which eclipsed it as the premiere Greek city in Egypt. Nature also dealt it another blow, as the Nile shifted. Its ruins today are found near Nebireh, El Nibeira, 75 km south-east of Alexandria.
 Some sources speculate that possible birth and death dates might be c.170–c.230 AD.
 PDF Book link valid as of Feb 2007; please report to CooksInfo.com if you find it has gone invalid.
Etymology of the word "deipnosophistae": in Classical Greek, "depnon" ("το Δειπνον") means "meal" (in Athens, it meant more precisely the main meal of the day, e.g. dinner.) "Sofistay" ("σοφισταί") meant "wise or learned ones", from whence our word "sophisticates". Thus, "deipno - sofistay", or "dinner sophisticates." Some people translate this into better English as "The Gastronomers", some as "Banquet of the Learned", closest of all might be the "Clever or Wise Dinner Guests" or "Dinner Table Philosophers."
As an aside, also building on the word "dinner" ("depnon"), in Classical Greek "depno-loxos" ("Δειπνο-λοχοσ") meant "to fish for an invitation for dinner." Some things really are timeless.