[Since] The Sum of Things must stand as the last novel in Olivia Manning's long and well-used career, it is still about contingent manouevres, but it is also, powerfully, about duration. In Manning's humane irony all events in life are radiantly fresh, but they are over quickly, their fulness is never quite used, and they never yield the knowledge which they tantalisingly might give if one knew where to look. So life continues until it is sliced off by death. Olivia Manning has managed to write that modern rarity, a philosophical novel formed entirely out of fragments of felt life. In The Sum of Things everything happens through people, even though the flares and barrages of history have put these people where they are….

The Sum of Things is a novel of incomplete recognitions. Vaguely trying, and equally vaguely failing, to understand, is the mark of a serious Manning character. The failure is almost always not recognized by the character and is usually not underlined by authorial comment; otherwise life couldn't go on. Beyond the more fully alive characters are the Egyptians, whose unstressed but repeatedly described object-status adds up to Manning's cold-eyed critique of the colonial world-view…. (p. 20)

Whatever Harriet, Guy, Angela, and Castlebar can learn and whatever they can feel for each other doesn't begin to free them from what Manning, in an earlier volume, called 'the bewildering inexpedience of life'. Life, however, isn't experienced as a trap. The sheer sensation of being young and alive in wartime is so strong that The Sum of Things reads like a thriller, in spite of what is at times a fairly sluggish plot….

All the major characters except Simon turn out to have extra resources, even if, as in life, explanations are few. Manning makes characters drift in and out of focus without precisely clarifying their dramatic or thematic function for the whole trilogy because they have an experiential function here and now…. Though Manning, with her usual tact, doesn't say so, the point is that through nobody's fault, even the most fascinating and promising friend may turn out to have a fate elsewhere.

Olivia Manning's best novels take place out of England. The Balkan Trilogy and the Levant Trilogy are set during the second world war in Bulgaria, Greece, Egypt, Syria and Palestine, all underused by novelists. Because she has resisted Durellesque exoticism, these settings give Manning's realism its characteristic combination of distance and ordinariness. In the Levant Trilogy's brilliant battle scenes, life's natural incoherence accelerates into a terrifying but supernaturally purposive chaos. In Manning's foreign settings each detail is special, so it can be presented economically, then met with again. Conversely the predictability of friends and lovers takes on a supportive familiarity….

The story continues, as most lives do, quietly and unpeacefully, with the important things never getting enough stress. Olivia Manning picked a good note on which to end. (p. 21)