The Doomsday Book starts with an intriguing idea, but misses the opportunity to truly entertain. As many other reviewers have pointed out, the major plot turns are driven by people not being able to contact each other, or fainting before they can reveal "the answer". This is extremely frustrating for a reader to encounter, over and over.
I wondered as I read, "why did Ms. Willis write this book? What's the point? After I finish it, what will I say this book did well?" The answer, apparently: to allow the reader to experience the desperation and hopelessness that plague-ravished towns in rural Europe went through during the 14th century. If the Amazon blurb had said this, I wouldn't have bought it.