Here are some of the spoilers you missed out on by not reading Animorphs:
Five children are forced to engage in guerilla warfare, espionage and repeated murder to protect their loved ones from alien parasites as they wait for the other, heroic aliens to finally arrive. When they do, the “good” aliens turn out to not give a shit about humans, caused the whole intergalactic war through their own shittiness and are willing to exterminate whole planets themselves to get at their hated enemies.
A child repeatedly experiences his intestines hanging out of his body while in various animal forms
A child is mentally tortured until broken and never gets better
A child in the form of a fly experiences getting splattered and smeared against a ceiling until his friends who are also flies at the time can peel his body off and take him somewhere he can transform back into a whole human before his insect mind fades completely
A child is shrunken and experiences having her eyeballs digested out of her head inside her friend’s stomach while she’s in the form of a tiny elephant
The heroes are forced to permanently imprison another child in the body of a rat because he knows too much and they abandon him on a tiny island with only other rats and garbage for company. Rumors circulate that the island is haunted but it’s actually his psychic screams reaching distant boaters.
A race of devastatingly powerful, violent aliens turn out to be mental toddlers who don’t know what they’re doing and are just bred to think they’re playing one big game before they’re killed at age three so they don’t learn the truth
An alien spends a few centuries hanging from the parasitic tentacle of a much bigger alien, surrounded by millions of rotting corpses attached to its other moon-spanning tendrils. They engage in mental warfare until one finally absorbs the other completely.
It turns out another seemingly “evil” alien race is simply driven to kill and eat everything in sight because it was separated from its original world where food was continuous and the entire specie’s life is the torture of perpetual starvation
A peaceful robot willingly removes its inhibition against violence to help in the war, only to slaughter a huge number of alien-controlled humans so gruesomely that nobody dares think about or speak of it again and it is the only thing left undescribed in a book series that already describes entrails getting torn out and skulls getting smashed
A child stays too long in the form of a flea and instead of turning back into a human, accidentally turns momentarily into one big, giant flea that can only writhe and moan because it shouldn’t exist and can’t live at that scale.
The kids discover Atlantis, then discover that Atlanteans are inbred mutants who paralyze any humans they find, dissect them alive to figure out how their organs work, then stuff the corpses as kitschy museum displays for their children.
An ordinary ant gets transformed into a human child. It has no idea what’s happening and is so overwhelmed by its huge new brain and sensory input that it can only scream until it dies
