An easy, "snack food" read. Not a whole lot to have to digest, but entertaining enough to pass the time on the bus or in the park.
I would have liked Willis to engage more with the ramifications of her historical time-travel both in the discipline of history and in society as a whole. Disappointingly, the sections of the book that focus on "21st century" Britain read very much like they take place in 1992, when the book was published. In this way, the scope and imaginative power of the book feels very narrow.
Another criticism is the one-dimensionality of the characters. Most (even the main characters) seem to have one defining personality characteristic: stubbornness, spunkiness, persistence, etc.
Nonetheless, a good thought experiment and firsthand tour through the dessimation of the plague in one small medieval community.