This was the theme of both books. Each followed the path of a hero forced through suffering at the hands of the gods. And both books recorded these legendary journeys in the form of epic poetry. Nonetheless, the books were very different at certain points, primarily in what they emphasize. The most notable difference was their storylines, which were drastically different. The Iliad concerned itself about one hero and his immature moping, while simultaneously tracking the feats and deeds performed by all the other heroes of the war; Aeneid rather followed the journey of a hero forced from his home and city who did everything in his power to keep control of his people by bringing them to the salvation and glory promised to him.
Slightly less noticeable was type of book each is. In a sense, The Iliad was slightly more character-driven, in that its primary story point was Achilles' changing of mind; Aeneid, on the other hand, focused more on the actions of Aeneas than on his character. Similarly, Homer was much more descriptive of every minute detail than Virgil. The Greek would use lengthy metaphors for practically every death in the battle and often spent entire chapters on a single day or hour of battle. Virgil was much more contemporary in that he focused more persistently on the storyline at hand rather than deviating.
Also, the two books had a different purpose, atmosphere, and feel about them. While The Iliad seemed to be more a narration of an actual event, The Aeneid makes itself more about promoting the Roman Empire. The one used a great amount of description to portray the time period, while the other used parts of the story the praise the glory of the author's motherland. In this way, the Greek version of the Trojan War felt more like a record of a historical landmark, while the Roman edition of the war's aftermath took more the form of propaganda in favor of the Empire.
Both books are epic, classic, and filled with battle.
