It's after the other three. Hang on, I'll write down what the blurb is:
"It is six months since the cataclysmic events of Abhorsen, six months Nicholas Sayre has spent recovering in Ancelstierre. But he is desperate to return to the old kingdom, and at last he has his chance.
All he has to do is spend a weekend in a country house as a favour for his Uncle Edward, Chief Minister of Ancelstierre. That seems easy enough, till he discovers that the house holds many secrets, and the worst of them is a relic of the old kingdom, too far from the Wall for any spark of it's magical life to reignite.
Unless someone fonds a way to unleash its power..."
That's it, word for word. It's very short, I finished it in about half an hour, but its still pretty good.
As this topic is kinda about Garth Nix as a whole (see topic title), has anyone read Mister Monday and Grim Tuesday? I have to say, I really enjoyed those.