Silent Night by Robert Parker and Helen Brann

When Robert Parker died suddenly in 2010, he was working on a Spenser Christmas novel. His long-time literary agent, Helen Brann, asked Parker's wife if she could finish the novel for him. The result is Silent Night. The story starts with a young kid showing up on Spenser's doorstep and asking him for help and ends with a wild dinner party, all taking place in the weeks before Christmas. It's a quick read and a good story.