As this will probably be my last book of January, this gets it's own spot.
Dead Famous by Ben Elton
Set in a Big Brother type TV studio a murder is committed but no-one can work out who-did-it, including the housemates! I love Elton's satirical style which I know is not for everyone, he chooses popular themes then rips them apart in his own inimitable way. This is certainly not his best yet still is an entertaining murder mystery full of satirical observation.