I just finished reading Immortality.
I really enjoyed this, particularly the concept, which I thought was brilliant. Seemingly randomly, hundreds of people in a single location all within a tight radius just die within a minute or so. It starts happening again and again, in larger and larger scale, and there is a race to discover just what is causing it and how to fix it. There is clearly a bacterium involved, but it just doesn't make sense.
The pacing is quite good given the novel is around 500 pages and the information about what is really happening is fed constantly so there are few boring patches. I liked the way a chapter would be devoted showing the lives of some characters only to have them die in a kill zone shortly afterwards. It was a little USA focused but hey, you get that.