Mine is the wings of fire series, it is a "kids" novel (think like warrior cats age range)
But Tui T sutherland is so good at writing characters and introducing and describing worlds and characters that i reread it every so often. Like, she managed to write a book from the pov of a mind reader and it works.
Every book is from a different character's pov and each character feels wholly unique.
The main issue with the series is that the plot is kinda average at best, the characters really carry the story.
The Harry Potter main series, for which I have a major case of nostalgia. I'll happily and accurately slag JKR off for being a dimwit with terribly stupid opinions, who would need to be both smarter and more committed to make her "make it up as you go along" worldbuilding make any sort of sense at all. Which, bluntly, it doesn't.
But considering how much of a turnip she is, parts of her worldbuilding is strangely compelling while others fail basic self-consistency.