For the non dutchies:
This book (and the 2 others) are set in a world a thousand years from now. The earths ax has shifted and now Greenland has become green and lush (like Norway/Sweden now).
This country called Thule is ruled by women, men has absolute no say in anything. And they live green, no engines of any kind, no cars etc etc. Of course this works very well *g*.
Anyway far away in Europe things are a mess, droughts, wars etc etc. One country ( sounding suspiciously like Germany), the Baden empire want to colonise this country after finding it.
Three books later the Baden Empire is defeated and the countries decide to co exist next to each other.
In between loads of trips through wilderness, adventure, love, fun, sadness etc. Anything that will entertain a teenager.
I read these from the library and I was good friends with the manager there. When book 2 arrived I got to read the book before it was properly set up for library reading. I can still remember how happy and honoured I was.
Since then I bought the trilogy in hard copy and they are standing in my living room on an honoured spot in my cabinet.