YA 'Must Reads' -- help needed!

It's definitely YA, imo -- hits that 'experiencing something for the first time ever' core theme of YA perfectly. It's also fairly subtle in its portrayal of prejudice and mental health issues in a way that would be easier for an older audience to understand.

This page also covers a lot regarding mentions of sex, drugs, and swearing (that I'd forgotten happened tbh).

My recs:

Anything Rainbow Rowell

Anything Maureen Johnson

Chaos Walking trilogy by Patrick Ness (and they're making it a movie, so hurry up and read it first, haha!)

Andrew Smith!!!! Grasshopper Jungle, Winger, anything really...
We are the ants
Heather Demetrios--her books are great-- I'd suggest 'I'll meet you there' or 'Something Real'
Will Grayson, Will Grayson (John Green/David Leviathan)

FROST by Marianna Baer. It's an older one but it's awesome, especially if you like the boarding school scene.
WHEN by Victoria Laurie. I thought the idea of the story was a really cool one and she carried it out well.
THE STRANGER GAME by Cylin Busby. It's a creepy story based on true events. Has a good twist at the end.

Trying not to duplicate...
- Patrick Ness, THE REST OF US JUST LIVE HERE. Also A MONSTER CALLS, but it's shorter and I know you like longer stories... it's good, though.
- Neil Gaiman, CORALINE and THE GRAVEYARD BOOK.
- And if you don't finally read *something* by Terry Pratchett during this trip, you and I are going to have words. Since you're specifically looking for YA, I'll suggest A HAT FULL OF SKY THE WEE FREE MEN comes first, what the hell was I thinking?!?
- Nancy Garden, ANNIE ON MY MIND. Def. a should-have-read for LGBTQ YA.
- Eva Ibbotson... hard to pin down just one for this, I love all her books and they're definitely classics. My faves are the MG monstery-comedy ones, but I think... (spins roulette wheel)... JOURNEY TO THE RIVER SEA probably fits best into the YA should-have-read category. (I also strongly endorse THE STAR OF KAZAN, I've read it twice ).

ETA: based on input received - non-YA Pratchett. Can start anywhere, really, but for you I'd probably prescribe either SMALL GODS or HOGFATHER (since it'll be close to Christmas).