Part of about can't-even-count-how-many fandoms:
Keeper of the Lost Cities
Riordanverse (Percy Jackson and the Olympians, Heroes of Olympus, Trials of Apollo, Kane Chronicles, Magnus Chase, etc.)
Harry Potter
Fablehaven (& Dragonwatch) series
Divergent
The Remnant Chronicles
The Hunger Games
Maze Runner
Princess Diaries
Once Upon A Time (This one isn't a book, per se, but it's still amazing and it is a crime not to mention it, considering it qualifies as a fandom)
ACOTAR
Kings of Sin
Caraval (And A Curse for True Love, naturally)
The Cruel Prince
Six of Crows
Powerless
Fourth Wing
Throne of Glass
From Blood and Ash
The Fine Print
Zodiac Academy
A Shadow in the Ember
Dance of Thieves
The Selection
Lightlark
LegendBorn 
The Prison Healer
Shadow and Bone
Belladonna
City of Brass
Daughter of the Pirate King
Gild
The Atlas Six

AND MORE BECUZ LIKE OBVIOUSLY