The first outbreaks of the Black Death in Dorset. There is crime and secrets and lies, but this is counterbalanced by great kindness and cooperation and thought. You wouldn't think it could be a hopeful kind of book, but even as the plague strikes so swiftly with such high mortality, it does free up all the wealth and power that was gathered into so few hands.
Now I just have to wait for the story to be continued.
It's situations like this that make me reluctant to start a series until it's all written
Edited to add, 9/2/18: I often give authors of fiction about plagues a hard time for giving their imagined diseases an easy transmission, an incredibly high mortality rate, and a very brief latency: these three ratios all being very high means an infection will burn out in a population too quickly to spread. Even the worst plagues in naive populations don't score high on all three. They also tend to avoid people getting ill and recovering, which some portion of the population usually does. Most fiction wrlters avoid the importance of hygiene and sanitation and supportive care: they have everyone dying from the primary disease directly rather than address indirect mortality. I've encountered more than a few books that use 99.99% in order to decrease the surplus population. I mention this because I can only think of two writers who don't cheat that way: Connie Willis and now Minette Walters. If you want realistic plagues, these are the women to read.