The Hour of Death by Jane Willan
I picked up The Hour of Death because of its Christmas-time setting. It's the second in the series, but the first I've read and it worked fine. I felt like I got to know the characters well. I got enough background but not too much.
I enjoyed Sister Agatha for the most part. She's smart and tenacious, if a bit overly suspicious. Amateur sleuths pretty much have to be though. I could have done without her constant reference to other fictional detectives. Don't get me wrong, I adore Gamache and Jessica Fletcher, but she referred to them way too often. She stands on her own well, she doesn't constantly need to refer to other detectives. The nuns are an interesting group of women. While they do pray and sing and worship, they also make cheese and text each other and have an artist as a tenant. I think the Advent touches were some of my favorites: the hymns, the idea...
