Unnatural Causes is early Adam Dalgleish. He's still coping with his reluctance to become emotionally intimate and uses a holiday to visit his Aunt Jane as an opportunity to think things over. Will he ask Deborah Riscoe to marry him . . . or not?
Naturally, as soon as he arrives there's a mysterious disappearance followed by all kinds of bizarre events. When the mystery turns into apparent crime, Dalgleish becomes concerned for his aunt who doesn't have an alibi. A.D. is also on the outside looking in as the local CID led by Inspector Reckless seems to resent Dalgleish's presence.
The whole circumstance is made ore bizarre by the presence of many literary types in what increasingly seems to be a literary mystery written about in a mystery. There's a fascinating story within the story element that gets the book off to a strong start.
But as Dalgleish unravels the ultimate mystery, the book also comes unraveled. You get a lengthy explanation, but the end doesn't move swimmingly along like the beginning and middle do.
Perhaps Baroness James painted herself into a corner by producing such an imaginative mystery and couldn't bear to part with it when she couldn't think up a nice ending to match.
But I still recommend the book because of the strong beginning and middle. You can skip the end after the storm if you want. You'll probably like the book better if you do.