I recently watched (most of) this 2006 film on t.v. having, within the last year, re-read P.D.James' novel of the same name. They cannot be compared. I am sorry to be a "dissenter"from the surprising, to me, number of positive comments, but I think the box office returns say it all.
The novel, in all its quiet horror, suspense, thoughtfulness and subtlety did not deserve to be so distorted. Only the title of the film and the names of some characters are the same as in the novel. All the rest, the societal background, the political system, the response to the female (vis. male, in the novel!) infertility, the overall plot and characterization, is altered. The film, in my view, is just an excuse, yet again, for a showing of messy and unnecessary violence. Shame.