Overview
As usual with George, the mystery itself is well devised and a lot of fun to speculate on as you read.
You don't think of the Agatha Christie style of novel as being overhauled, but in fact, a number of very good writers have been pushing the cozy into some brave new areas. Nancy Pickard, Joan Hess, and Carolyn Hart, to name just a few, have demonstrated that the cozy can be serious as well as seriously (or pointedly, if you prefer) funny.
Over the past decade, Elizabeth George has also been pushing the Christie-style mystery into richer and more rewarding areas. Her new novel, In Pursuit of the Proper Sinner, is so rich in character, incident, and theme that one finally has to take it seriously, not just as a mystery but as a novel as well. I'm not going to say that it "transcends the mystery genre," because that's offensive to mystery writers. And rightly so. But I will say that, in much the same way that Sharyn McCrumb has expanded the range of the serious crime novel, George has also pushed her particular form to the limits.