SPOILER WARNING
Whoa, I was just going skimming through book 54 and I noticed this line:
Terrorism had grown as a problem. Many of the worst were religious cults convinced that the presence of alien species on Earth was delaying a hoped-for Armageddon.
Book 54, as the ending, is closing the book on the overall story and its themes. So for that reason this line has extra resonance.
And right at the very end, there is this language:
Weird to see that wild, messianic glow in the eyes of a man you knew was really just a Yeerk slave. It was a disturbingly human expression.
Animorphs was filled with commentary about human nature. That line is the last direct comment on the subject.
And then there's the description of The One:
The face that filled the screen and more was a shifting image, a slow dissolve from what might be a robot's face, a machine with a rat-trap mouth and steel eyes, into a sweet, feminine, almost elfin visage...
The appearance of The One is a trap. One form is beautiful and alluring, another is terrifying. This reminds me of a scene from Everworld book 9 involving Senna, who uses religion as a tool. Senna appears to dwarves as a beautiful goddess, and the dwarves refer to her as the Lady. She convinces the dwarves to trust her, which they do, and then her group destroys the dwarves.
Jake stared back at the foul thing on the screen. I saw what he saw, and I felt as if my brain was shutting down. In that shifting alien face was every corruption, every evil, and such power that it seemed impossible it could be present in just the narrow confines of the onrushing Blade ship.
Remember the emphasis Animorphs placed on not letting your brain shut down.
It's a little chilling, and sad, how book 54 saw the rise of religion-inspired terrorism in the Animorphs universe, and four months later 9/11 occurred.