". . . Homer has imposed a form which is clarity itself. The masterstroke, as Horace pointed out, was the decision to begin in medias res - in fact, near the end, with Odysseus, already for seven years a prisoner, now on the point of being set free. This, the starting point, is made clear with great brevity; very cunningly Homer keeps back the story of Odysseus's wanderings, those of the past and those to come, so that we may have them in an unbroken sequence. For the tale of the past wanderings he contrives the perfect setting: it is told by the suffering hero himself, and to an audience that has dined well, has been enormously impressed by the stranger . . . and is prepared to listen, if need be all night. This half of the material is enfolded within the other half - all that concerns Ithaca and Telemachus . . . The poem is made to circle around itself . . . "
From "The Odyssey: The Exclusion of Surprise" by D. H. Kitto