H20 by Virginia Bergin
Ruby has had a pretty normal life, until one day, while she is at her friends house, it starts to rain. They turn on the radio to hear the warnings; "It's the rain, it's fatal, it's contagious, and there is no cure." It's almost too hard to believe. But then someone goes outside.
Most of the population has died from the rain. Non-contaminated water is running out, and Ruby is stuck by herself to try to figure out a way to get back to her family, if they are even still alive.
I really enjoyed this book. There was a lot of humor, for such a gory topic, and it was overall very well written.