the neverending story was probably one of the most influential books i read as a kid. i was 11-12 at the time and something about the oncoming legacy of adolescence meant it just resonated so strongly. the copy i have is my mother's childhood copy, so it also has a lot of sentimental value to me.
on a similar note, the ocean at the end of the lane by neil gaiman was great. as far as gaiman works go i think it's underrated, because boy did that book make me feel things. i think very few books quite capture children's perspectives as well as it. it's also not lacking in dark overtones, and the nostalgic feel of it works very well.
the last unicorn by peter beagle fucked me up (in a good way) as a child and remains one of my favourite films. something about an immortal being that (temporarily) becomes mortal and must then live forever with the burden of having felt despair and loss, among a species that are otherwise naive about those things, is fucking metal as shit. the book was also great. if i ever have kids, they're getting onto this early, because it's so good. it had some scary scenes as a child, but the true horror was the emotional conflict and existentialism the characters faced, and i can honestly say it's one of the single most influential works of my life. it also bends a fair few conventions for a story from the 80s, like the knight in shining armour not getting the princess. the red bull remains one of my favourite monsters ever just by virtue of how well it was conveyed.
jurassic park was an absolute bop and i love it, film and book.
sharp teeth by toby barlow, while not *the greatest* story, did have a big impact on my perception of stories. it's a novel written in free style prose, it did a lot to shake up my ideas of what books could and should be. also the story was wild fun (werewolf power struggles in modern day las angeles)