From the Introduction:
"Unlike most of the FRP campaign supplements available on the market, The Lexicon presents an entire world for the players and Game Judges to explore. In addition to the many different countries and territories delineated in the text, The Lexicon contains five of the largest cities..."
"Another interesting aspect of The Lexicon is that all of the places and cultures described in the book either existed or were at one time believed to have existed."
The world map presented in The Lexicon is that of the Earth at a much earlier time. The sea level is higher, so the coastlines of the continents are much different (e.g., Africa has an inland ocean, the Sahara Sea), and continents have drifted (e.g., the land forming the modern day Middle East is disconnected from what is now India and the rest of Asia). In addition to Atlantis, many other legendary lands are present: Mu, Lemuria, Gondwana, Jotunland, Hyperborea, etc. Culture inhabiting the area receives approximately a one page overview, but they are left intentionally vague for players and game masters to flesh out.
The Lexicon is not designed for any particular RPG. As such, there are no player of non-player character stats or mechanics.