I can't believe I haven't posted here.
And seeing Sassy's name near the top gave me a pang.
As anyone who knows me for any length of time (4 minutes) knows I am a huge fan of Terry Pratchett's. His books for children and young adults are as fun and thoughtful as his adult stories, but I think written with better care.
The Bromeliad Trilogy (U.S. title) -
Truckers, Diggers, Wings - is the story of four-inch-tall people trying first to find a place in the human world, and then to find a home of their own. 8 and up, I'd say.
Nation - for a thoughtful preteen and up, a story of a boy named Mau, the only survivor of a tidal wave that sweeps away his island Nation, joined by an English girl of a scientific mindset who survives a shipwreck. Does not go where you think it might, dark in places, but full of light and hope.
The Johnny Maxwell trilogy, about a boy who sees things others do not.
Only You Can Save Mankind - Johnny is shooting up the aliens in his computer game. Then the aliens surrender.
Johnny and The Dead - Johnny and friends try to save a cemetery from being turned into a shopping mall, while teaching the denizens to dance to The Thriller.
Johnny and the Bomb - the best time travel story ever, where Johnny and friends go back to the WWII and the day when their town was bombed.
Set in the Discworld:
The standalone,
The Amazing Maurice and His Educated Rodents is the story of the Pied Piper, where the rats are in on the sting.
The Tiffany Aching books, the story of a young witch and her friends, the pictsies (not pixies, very definitely not), tiny blue men of a vaguely Scottish persuasion.
Wee Free Men
A Hat Full of Sky
Wintersmith
I Shall Wear Midnight
Impressive. Every word in that sentence was wrong.
Luke Skywalker, The Last Jedi