Like The Amazing Maurice and his Educated Rodents, which I
reviewed some time back, The Wee Free Men is a Discworld novel
slanted towards younger readers. It concerns a very young, very determined
dairy maid in oversized boots who’s the only one up to handling a bad case
of the Elves. Experienced Discworlders will know what that means, and
what kind of person it takes to handle it (and indeed, Granny Weatherwax
has brief cameo).

Terry Pratchett knows what it means to write for young readers.
The Wee Free Men is toned down a bit from his regular
Discworld books, but it isn’t dumbed down, and it doesn’t talk down. I
enjoyed it thoroughly. And in fact, it might be a remarkably good place
for you to start, if you’ve not encountered the Discworld before.