In broad terms the books are an intense study of the origin of the mythology of the Great Flood as well as the history of measure. Chapters 13 & 14 of Deluge are devoted to the story of Atlantis. Both books can be read online(a).While dealing with specifics such as, the etymology of Atlantis, Orichalcum and the Pillars of Heracles, I think the authors unusual conclusion is best expressed in their own words;
“It is found then, that Plato’s Atlantis ultimately is no more than another rendition of the ‘Great Flood’ mythology, in this case utilised by him to illustrate his importance in lawgiving. If the Ten Commandmentswere given to Adam and Eve instead of Moses then there would be a direct Biblical comparison. In essence, the story of Atlantis reinforces the analysis of the flood and creation legends as outlined in Deluge as in addition to the celestial events described therein, there is the devastation caused by known flood events at Sundaland to which his description decidedly points, some 11,000 years ago. This approximate date is dictated not merely by Plato’s ‘9,000 years’ for Atlantis’s demise, but also his depiction of its City and its central mound [the World Mountain supporting the axis of the heavens] as symbolically representing the constellation of Hercules when Tau Hercules was the Pole Star.”
Silvertsen and Redman were guest authors on Graham Hancock’s website with a paper(b) entitled Science versus Religion.