Storyline: 4/5 
 Characters: 4/5 
 Writing Style: 3/5 
 World: 3/5 
 An engrossing story, all the more so because Willis was so adept with tragedy. 
 This was, without a doubt, the most serious and somber time travel book I've come across. That is not at all a bad thing. Willis was compelling with almost everything she attempted here: the medieval historical fiction story, the futuristic comic musings, criticism of historical authority, child characters, and parallelism. 
 I think of there being three ways to approach time travel in your novel: 1) seriously consider and work out the paradoxes and mechanisms 2) sleight of hand and technobabble to obscure that you don't really understand it yourself but want the reader to think otherwise, and 3) avoidance - leave the details undiscussed, admit that you don't know, or baldly state that the universe or the mechanism simple operates this way. Willis opts for number three. I would rather my science fiction had opted for number one. There were a few other areas where I felt the story was wanting. Some of the dramatic license she took verged on the absurdly comedic for the overuse (view spoiler)[ Waiting for Badri to finish his cliff-hanger of a conversation with Dunworthy for hundreds of pages (hide spoiler)]. The near future was filled with interesting anecdotes and details yet it was overwhelmed by the attention given to the past. I expected and would have liked more from the "Doomsday Book," the book within the book. There were also some artistic parallels between past and future (view spoiler)[Dunworthy/God; Collin/Rosemunde; modern safety/ancient insecurity; contemporary doomsday sayers/medieval mysticism; hospital doctors/village priests (hide spoiler)], but I felt it was more for the sake of symmetry than it was to say anything substantive. Still, Willis told a good story. I was invested in the characters, I was interested in the environs, cared about what was going to happen, chuckled, grieved, and was generally able to suspend disbelief in the the right amount. I can see why this won both the Hugo and Nebula awards.