Wreck the Halls by Sarah Graves

"People hardly ever lock their doors in Eastport. So when Jake and her best pal, Ellie, arrive at Faye Anne Carmody's kitchen door, they knock and walk right in. But though Christmas is just two weeks away, what they find is far from festive: a dazed Faye Anne covered with blood, and her no-good husband - the town butcher, Merle - nowhere in sight. Nowhere, that is, until Jake discovers his body - tidily wrapped in his own butcher paper..." "It doesn't take long for news of the murder to race through the small town, and just about everyone has a theory about the grisly crime that has robbed Eastport of its least-liked citizen. But while police chief Bob Arnold considers it an open-and-shut case, Jake and Ellie aren't convinced of Faye Anne's guilt." "Jake has enough going on in her life without trying to investigate a murder.