Rumor has it that this will be the last Dalgliesh mystery. If so, James has given her detective a fitting last case. The mystery, as always, is secondary to the interior life of the characters.
One of my quibbles about series books is that readers of later books are expected to know more about the usual habits of the characters than that book wants to give away. This book doesn't have a lot of that, which is to James' credit.