I would actually recommend Michael Crichton for an 11-year-old rather than King.

Jurassic Park, Sphere, Congo, Andromeda Strain; all fantastic novels that will be interesting without traumatizing a young reader.

I read King’s The Stand at age 11, and about halfway through it, I literally remember thinking, “I might be too young to be reading this…” If you are set on introducing King, Thinner is all right, but I think King’s writing is really best for teens (like 16+) and older.

I would recommend Eyes of the Dragon, The Institute, The Talisman, Fairy Tale, and some of the short story and novella collections. I don't think you should worry about what is representative of King but what is relatable and good reading for an 11 year old.

I would recommend against Pet Semetary. I read it at around 11 or 12 and was very disturbed by it.

I read my first King book at that age: IT. I'm not sure I'd recommend it for a child of that age, though.

The girl that loved Tom Gordon. It’s not very long has a 9 year old protagonist and even if it wouldn’t have a monster it would be still a page turner.

I don't know why these haven't been mentioned on here but his short story collections are perfect. Night Shift, Skeleton Crew, and Different Seasons. You cover so many great stories in bite-sized chunks.

First Stephen King book I ever read was around that age. Through The Eyes of the Dragon. King wanted to write a medieval fantasy novel for his daughter. Personally, I loved it.

That said, if your kid isn’t afraid of a meaty book, It is also a great choice because it really captures how kids can be isolated for traumatic experiences, but can overcome it together. So in my opinion, that made it really relatable when I read it around the same age. It does have that weird child sex orgy in the middle, but reading King is never a good way to avoid reading fucked up shit.

My personal favourite of King though is the Dark Tower series. The Gunslinger is the smallest entry in the main series, so it’s easily readable.

The first and third option aren’t pure horror like It, but IMO that’s what makes them great, because you get little sprinklings of horror, which can make it creepier because it contrasts (without feeling unnatural) with the rest.

Don’t try to force it, just mention you enjoyed reading his books as a kid.