Two children from nations at war with each other find themselves in the same "school of knights," and learn to use their individual aspirations in the service of their group, rather than that of their selfishness. It is the overall beautiful lesson drawn from.
Narrative side, we have here a world that seems initially Manichean and who is ultimately less gradually as the plot forward: despite the presence of elves, trolls and goblins, this world is very human, full of nuances.
The progression of the two heroes is not linear, and often takes the opposite of what is expected, what is for the best. And while I was starting to yet another fantasy pad, it was hard to let go of pages: strongly later, to know what happens Gischild and Luke.