Extraterrestrial Life
More so than any other novel in this series, The Atlantis World reveals just how small humanity is in the grand scope of all extraterrestrial civilizations. The Atlanteans have been portrayed as an ancient, advanced, technologically superior civilization, but even they felt small next to the Serpentine Army, a giant mind-army that assimilates people and spacecraft into itself to grow stronger. There are mentions of several more alien races and populations, and the proportions of the universe grow exponentially with each new discovery. In the face of all of these civilizations, humanity seems small and pathetic. The signals of extraterrestrial life Mary detects at the beginning of the novel, moreover, reveals the significant effects of alien life on the book's action and plot.
Racing Against Time
Racing against time is another major theme of this tense, thrilling novel. There are multiple timelines the protagonists are having to deal with simultaneously: Ares is about to unleash a global flood on the world, the Immari are threatening civilizations again, and the Serpentine Army is on its way to Earth to destroy it and assimilate its inhabitants. On top of all that, Kate only has somewhere between four and seven days to live due to her "resurrection sickness." The novel's heroes must complete all of their objectives before these realities come to pass if they wish to save the human race.
Preserving Humanity
The ultimate goal of this novel, and a theme that continually reveals itself in the plot, is the preservation of the human race. This has been a theme throughout the series; just in the last book, Kate saved humanity from the deadly outbreak known as the Atlantis plague. Here, though, the stakes are even higher: the Serpentine Army is on its way to destroy the whole planet. In addition to this extraterrestrial threat, Ares tries to unleash chaos on humanity in order to create a human with a resistant enough will to fight back against the Serpentine Army's assimilation, and the Immari are threatening to kill tons of people in their plans for world dominance. In opposition to all of these threats, Kate and her friends are fighting to save humanity both from itself and from the outside forces from around the universe.
