The book, for those who don't know, keeps almost all of Jane Austen's original text, adding in sections (and changing just a few words here and there) to add a background of a zombie plague across England, where the five Bennett girls (and Mr. Darcy, although not Mr. Bingley) are all well-trained in zombie fighting.
Aside from my enjoyment of the zombie element, I very much appreciated the way that it made several pieces of the plot easier to understand. Charlotte's decision to marry Mr. Collins, for example, stems not just from her fear of ending up an old maid, but also from her infection with the zombie plague, her awareness that she has but a few months to live, and her hope that her new situation will give her a better end. Darcy's excuse that he warned Mr. Bingley off of Jane because he feared that her illness (from Jane Austen's original) might be a sign that she had also become infected with the zombie plague also is much more believable than that he feared she wasn't actually interested in him.
In all, a very enjoyable book; the solidly 1900-era costumes on the girls in the illustrations aside, I heartily recommend it.