Troubletwisters: Book 1 - Garth Nix

Jaide and Jack Shield's lives are changing in a very, very strange way. The weather is turning against them. Magical disasters occur when they're around. And a mysterious explosion has just destroyed their house...from the inside.
Without knowing why, the twins are stolen away to live with Grandma X--a relative they've never, ever met. At Grandma X's house, things are even stranger. Weather vanes point in the opposite direction of the wind. Doors appear and disappear. Cats talk.
Jaide and Jack don't know the reason behind all this strangeness. They don't know that they're troubletwisters, and that they must defend the world against a dark, evil force. The time has come for them to discover the truth--and the powers that come with the truth.
Are they ready?