The Warning was another book where I had that deja vu feeling. I don't remember reading this one as a kid, but maybe I read a friend's copy once or something. It is definitely the creepiest Animorphs book so far.*
It starts out normally. I had to ignore all the computer stuff at the beginning because if I hadn't I might have started laughing and never stopped. The computer stuff also brought up so many questions about security and surveillance, but I have to stop falling down that rabbit hole because it's there in every book.**
This is a book that sort of goes into morality during war but it's not a great example. More discussion with spoilers under the cut.
So we're in a Jake book and this is the kid who 1. is the reluctant leader but 2. was totally willing to boil hundreds of Yeerks in his second book. Granted they were hostless, I thought that might come up at some point in this book, but nope.
*In this book we have a graphic description of Jake swatted in fly morph, an online predator/pedophile who's targeting Marco, several human security guards trampled, a cannibalistic Yeerk and an arsonist in the Animorphs.
** How did Jake know the correct spelling of the word Yeerk?