is he portrayed in literature?
Yes, in the "Divine Comedy", Dante sees Guiscard's spirit in the Heaven of Mars
Robert Guiscard
In the "Divine Comedy", Dante sees Guiscard's spirit in the Heaven of Mars, along with other "warriors of the faith" who exemplify the cardinal virtue of fortitude. 
where did the battle of dyrrhachium take place? The battle was fought outside the city of Dyrrhachium, the major Byzantine stronghold in the western Balkans, and ended in a Norman victory. between whom did it take place? The Byzantine Empire, led by the Emperor Alexios I Komnenos , and the Normans of southern Italy under Robert Guiscard, Duke of Apulia and Calabria. when did the latter come into power? 1058
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Robert Guiscard [SEP] In literature
In the "Divine Comedy", Dante sees Guiscard's spirit in the Heaven of Mars, along with other "warriors of the faith" who exemplify the cardinal virtue of fortitude. In the "Inferno", Dante describes Guiscard's enemies as a field of mutilated shades stretching out to the horizon. Guiscard was the protagonist of Kleist's verse drama "Robert Guiskard", incomplete at the author's death (1811). Historical fiction novels covering the early years of the dynasty, from the arrival of the brothers in Italy to the conquest of Sicily, is covered in Jack Ludlow's trilogy "Mercenaries, Warriors" and "Conquest".