This is a crabby book that attempts to refute the legend of Atlantis and other lost continents with whatever method it can muster - geology, geography, literature and "scientific." It doesn't quite live up to it's reputation, although it has a lot of interesting maps in it and makes some good points about continental drift and other scientific theories. On the one hand, de Camp has done a lot of research for it and brings to light, although I am sure unintentionally, some valuable history on how the Atlantis story came into being (mainly references to it before and after Plato). His conclusions on what scholars knew and thought at the time are subjective at best, though and, since the book was written back in 1954 and only slightly revised in 1970, according to the jacket, much of the points he makes abour scientific research are now dated.
The main fault in the book lies in the title itself. De Camp's main points are that a continent as big as Atlantis was reputed to be couldn't have sunk, but the original account from Plato didn't clearly call Atlantis a continent, and there is plenty of evidence of similar land masses of this smaller type sinking (some brought up by de Camp himself in the book, like the island of Krakatow). Since none if us were alive in the past, how can any of us be certain what the land masses looked like then..? His other point is that people were not even advanced enough to have built Atlantis back in 9,600 b.c. (he describes our ancestors as "sitting on a branch and scratching" at that time). De Camp, at the time anyway, seems to have bought wholesale into the Darwin theory of evolution, which, we know now, has plenty of holes. These days, as more discoveries have been unearthed, the date for human civilization is being pushed back more and more. Ruins have been found on Malta that date to 8,000 b.c. and even the Sphinx has been redated, albeit not by everyone, to 10,000 b.c. Underwater ruins discovered off of Cuba have been dated to 15,000, even 30,000 b.c. Also, I am shocked by how little research was done when trying to dispute the most popular theory of Atlantis - the Atlantis sinking beneath the Atlantic theory (a scientist friend of his lowered his camera down by the Mid-Atlantic Ridge with a camera and didn't see any ruins there) ...
His evidence to dispute linguistic evidence of Atlantis, as well as Atlantis and the Mayans connection, all needs more time to answer than I care to give here, other than to say, he is very selective about the examples he gives to prove his case. His research into the almost equally legendary isle Antillia actually proves it's existence rather than disproves it the closer one looks at it. And there are many other parts where de Camp simply dismisses a whole researcher's body of work by calling them loonies (this from a guy who for the most part made his name writing Conan the Barbarian novels, some of which starts out "before the oceans drank Atlantis...").
A cynical work that brings forth the occasional good point about Atlantis, perhaps the bible for the anti-Atlantis people.