If you like Lemony Snicket...

...I bet you would like The Kneebone Boy by Ellen Potter.  Otto (who never speaks and refuses to take off his scarf), Lucia, and Max are the Hardscrabble siblings.  Their mom mysteriously disappeared five years ago, and their father goes on faraway trips to paint portraits of royalty who...aren't quite so royal any more.  The kids are on a quest to find their mother, and they end up at Snoring-by-the-Sea, with a pretty cool great-aunt who's staying at a "castle folly" - a life-size children's castle full of mystery and secret passages.  A few British terms may be unfamiliar ("torch" = flashlight; "trainers" = gym shoes), but the reader will still enjoy plenty of cleverness, humor, and adventure.  The ending is definitely not Lemony Snicket-y; instead, it was unexpected and bittersweet, but still quite satisfying.