The Sum of Things is the final volume of [Olivia Manning's] Levant Trilogy (itself a continuation of the Balkan Trilogy)….

[There] is clearly a problem in writing "series" novels in which the same characters recur, especially if, as in this case, each novel is designed to stand independently. How much characterization can be taken for granted? Must physical descriptions be given all over again?

Olivia Manning repeats an awful lot….

The major and constant theme of the trilogy is the uneasy relationship between Guy and Harriet, stranded in the Middle East during the Second World War. But there is in this final book one striking difference, and it is this difference that forces one to see the book as overwhelmingly concerned with disappearance, death, loneliness and loss: the two main characters are separated for most of the time….

Both Guy and Harriet pass through ordeals of solitude—though neither is often alone—in which they assess themselves and each other….

[Harriet has changed] and Guy's very deficiencies now allow her self-determination—to think her own thoughts and see her own friends, even though like Guy she is reconciled to marriage: "In an imperfect world, marriage was a matter of making do with what one had chosen." This is wisdom perhaps—but the conventional wisdom. Hardly a crowd-stopper….

One has to harp on the relations between these two because the author does. But this is not traditional "women's writing"; Olivia Manning writes sexlessly about sexual relationships, and the setting, the rackety wartime atmosphere and the documentary flavour of the Levant Trilogy cannot be overstressed….

The Sum of Things adds up to sadness; it is a feat of resignation rather than resolution, and the one happy couple in the book, the illicit lovers, are parted by a needless death that parallels the gratuitous horror with which the trilogy began.