The League of Beastly Dreadfuls by Holly Grant, 294 pages

Anastasia is a completely average almost-eleven-year-old. That is, UNTIL her parents die in a tragic vacuum-cleaner accident. UNTIL she's rescued by two long-lost great-aunties. And UNTIL she's taken to their delightful and, er, "authentic" Victorian home, St. Agony's Asylum for the Criminally Insane.
There, Anastasia's aunties give her everything a girl could want: a cozy room (is that a chamber pot under the bed?), sumptuous meals (mmmmm......Mystery Lumps!), and character-building responsibilities (catching leeches!).
But something STRANGE is going on at the asylum. Are those attack poodles in the garden? Is it ODD that her aunties wear the same ring as the EVIL school secretary? And why, for goodness' sake, do they collect pictures of MISSING children?
Anastasia soon begins to suspect that her aunties are NOT who they say they are. So when she meets Quentin and Ollie, two mysterious brothers, the three join to plot their great escape!