Why do you go away? So that you can come back. So that you can see the place you came from with new eyes and extra colors. And the people there see you differently, too. Coming back to where you started is not the same as never leaving.
A Hat Full of Sky takes and grows from there, following Tiffany Aching as she actually starts to learn a bit more witching, while at the same time having to deal with some of the fall out from her actions in The Wee Free Men.
She’s actually got someone teaching her now: specifically Miss Level, who is a bizarrely wonderful character, the exact sort of thing Pratchett does well in Discworld. Minor spoilers, but she is one mind living in two different bodies , which leads to all sorts of interesting comments and situations before Tiffany puts it all together.
Plotwise, the big bad this time around is an invisible beastie that’s been chasing Tiffany and is keen to pray on her burgeoning Witch powers that no one quite expects her to have yet, so don’t adequately explain. It’s an interesting take on a coming of age / coming into yourself story, and well done.
Technically, it’s still a young adult book (and Tiffany is still a young girl –a teen or perhaps even pre-teen, I’m not entirely certain), but it’s a pretty intense book at times ( those taken over by the beastie have a tendency to end up dead... ). I don’t like it quite as much as The Wee Free Men, but that’s not saying overly much. They’re both well worth the read.