As for the site of Troy itself, researchers have found that descriptions in Homers "Iliad" coincide with their findings, which is more than the film's representation can say. Troy, or Ilium, existed on the West Coast of what is modern day Turkey, around 1200 BC. There are many layers of strata and evidence suggesting that Ilium was indeed attacked and burned to the ground. Hittite texts also make reference to the characters of Homer's "Iliad" and a possible war. Archaeologists are still questioning their finds and searching for evidence to support or disprove the many theories that evolve around Troy.
Between the book and the film there are a wealth of differences, and similarities only lie in the basic, undisputed ideas. "The Iliad" begins in the ninth year of the ten year siege of the Greeks upon Troy, whereas the movie shows Paris taking Helen away from Troy angering Menelaus in the process. The Greeks sail across the Aegean Sea (in ships of a questionable eighth century design www.archaeology.org/onlinereviews/troy) for vengeance upon Priam's Kingdom, with the assistance of Achilles. Fighting and bloodshed follow, culminating in the well-known wooden horse stealth attack and the burning of Troy. This part of the myth is told in "The Aenead", as "The Iliad" ends with Hector's funeral - a main difference between the two texts.
Another obvious difference is the absence of divine intervention of the Greek gods in the film, or indeed any direct evidence of their presence. As the gods where what made the ten year war come to pass in the first place making "The Iliad" an epic battle of wills, "Troy" falls short of providing this resonance to its audience, and also lacks credibility in its plot. The catalyst of the war was triggered by Aphrodite when she promised to beautiful Helen of Sparta to Paris. She shields the lovers from Menelaus's gaze, and when the battle between Menelaus and Paris takes place, transfers Paris to the safety of Helens bedchamber (Book 6 pg 106). As the movie can't do this Hector has to save Paris instead.
Intervention by the gods as the assist their favourite mortals is a big theme in "The Iliad", helping to explain how certain instances take place. For example, King Priam walking into the Greek camp seeking Hector's body. In "The Iliad" he is guided by the god Hermes by order of Zeus "The Wayfinder, showered a mist of slumber on them [the sentries]" (Book 24 pg 432), but in the film Priam merely says "I think I know my country better than the Greeks". This is where "Troy" lacks credibility and needs to explain how occurrences such as these take place, if they will not involve gods at all.
Who kills who is another questionable factor in "Troy". As mentioned, Hector intervenes and saves Paris from Menelaus, stabbing him. In ancient tales Menelaus returns to Sparta taking Helen with him when he plunders Troy. Another such instance is when Brisies ( a slave girl for Achilles in the book, but a priestess of Apollo, Priam's niece in the film" stabs Agamemnon. He too was supposed to survive the war and return home to Greece to be killed by his wife Clytemnestra. Scenes like these are necessary to...