In The Great Hamster Massacre by Katie Davies, Anna and her little brother, Tom, have been begging their parents for a pet other than New Cat (their slightly crazy, kind-of evil cat), but their mom has said NO every time.   When Anna's grandmother dies, Anna's mom finally gives in and allows them to each get a hamster.   Happiness ensues and the hamsters, named Number One and Number Two, fit into the family well (although New Cat gives them some hungry looks). 

One morning, Anna and Tom wake up to discover that a HAMSTER MASSACRE has taken place overnight (warning: the brief descriptions of the carnage are a little gruesome).  Who, or what, is responsible for the hamster deaths?  It's up to Anna, Tom, and Anna's friend, Suzanne, to investigate.  This very funny British book is full of wacky characters (Mr. Tucker, the neighbor who calls people, "old chum," is my favorite), ridiculous events, and hilarious illustrations.