I finished the novel, and I'm left feeling...what? Unsatisfied? Misled? James' "Prologue" is, indeed, rather brilliant, and for me, it may be the highlight of the book. The rest of the novel proper doesn't contain that same Austen-esque wit and style. While P.D. James is obviously quite familiar with the social conventions of Austen's time, the style of the book just isn't as lively (as either Austen or James' own prologue). In fact, the opening chapters seem to have a Bronte influence*, a touch of the Gothic, "on a dark and stormy night" filled with foreboding until the actual murder is announced.
Now my misgivings with the book may be due entirely to genre; James is writing a murder mystery, not a drawing room comedy. Her style might be entirely suited to the murder mystery genre. I wouldn't know; I'm not a murder mystery afficianado and haven't been since I was obsessed with Lilian Jackson Braun's The Cat Who books in junior high. It all felt much too fast-paced, but again, mystery book, not regency romance. The resolution of James' plot is (un)suitably complicated and convoluted. Is this typical for mystery? It felt more like the wrapping up of loose ends in a farce than a period mystery.
More than that, though, is the fact that James' relationship with these characters seems too close and almost too comfortable and casual. We are privy to their thoughts and feelings in a way we never are in Austen's world (especially Darcy). There is no slightly distant ironic narrator. I didn't care for that kind of relationship with the characters.
In short, the "Prologue" was the best part of the book for me.
(Snoopy courtesy of TVTropes.org)
*Don't misunderstand me. A touch of the Bronte is not considered a bad thing around here (pointing to Leonard's collection of Jane Eyre editions). I just wasn't expecting it in this book.