"The Iliad" should really be subtitled, "Achilles is an ass". That's basically what the story is about, from almost the very beginning to the last page: Achilles acting like a 3-year old throwing a temper tantrum for most of the length of the story.

Of course, this poem is 3000 years old and one of the oldest works of literature to survive that long; it's an amazing and highly influential work; and there is so much to be learned from it historically and culturally that it's an incredible work of art and pretty much essential to any education in literature.

But, nonetheless, if you ignore all that and just take the story for what it is, it's a long and fairly violent story about Achilles being a total dick and everyone suffering. Plus a lot of lengthy ancient Greek lineage recitations which, if you pick up the audio book, will make an excellent cure for insomnia in certain chapters.

I'd say spoilers, except it's hard to see how to spoil a 3000 year old story, so plot summary: during the war with the city of Troy, the Achaean soldiers capture a couple of pretty maidens from an allied town, and these poor ladies are given to King Agamemnon and Achilles (one of the greatest warriors) as "prizes". One of the maidens happens to be the daughter of a priest, who offers Agamemnon a huge ransom for her return, but King Agamemnon refuses because "MINE". Priest consults the god Apollo, who sends a plague down to punish King Agamemnon and the whole camp. Eventually Agamemnon gives the priest back his daughter, but then takes Achilles' maiden in her place because Kings can do that kind of thing, apparently.

Achilles has a temper tantrum worthy of a spoiled toddler and refuses to fight Troy or anyone else any more, because Agamemnon took "his" toy. With Achilles pouting in his tent the war starts to go badly and the Achaeans start to suffer badly. Insert various conflicts between various heroic characters on both sides, which the Greek gods aid and abet and generally confuse, switching sides so often (and sometimes working against each other on both sides) that it's hard to understand why either side could ever find it helpful to pray to any of them.

Defeat seeming imminent for the Achaeans, Achilles' best friend Patroclus persuades Achilles (still sulking and refusing to do anything) to let him wear Achilles' very recognizable armor and inspire the Achaeans to rally (assuming he is Achilles). He does this, and the Achaean morale improves enough to push the Trojans back to the city walls, but unfortunately Hector (the greatest warrior from Troy) kills Patroclus (aided and abetted by the gods).

Achilles, having basically caused the death of his best friend Patroclus by acting like a spoiled brat, finally rejoins the fight and goes on a rampage killing everyone he can, eventually including Hector (now betrayed by the gods, because you just can't trust those gods). Achilles then spends the next 10 days or so dragging Hector's body around tied to his chariot wailing about Patroclus's death and how sad he is (except for the part where he decides to throw a set of "funeral games" including chariot races and wrestling for prizes which Achilles provides), and generally trying to mutilate Hector's corpse as horribly as possible (which is foiled by those indecisive gods, who now - rather belatedly - pour healing salves and stuff on the corpse so it doesn't decay and still looks good).

Eventually even the gods agree this is getting ridiculous and Patroclus appears to Achilles in a dream telling him to give Hector's body back to his father, and the gods escort Hector's father the king of Troy to collect the body, which he does, having a nice dinner with Achilles in the mean time during which Achilles agrees to stop attacking Troy for a 2 week temporary truce so the Trojans can properly bury Hector. At which point the book ends, although Patroclus has made it clear in the dream that Achilles is about to die also, so Achilles spends a lot of time telling everyone how he wants to be buried with Patroclus and all the details of what he wants.

And thus ends my very irreverent but completely accurate plot summary of "The Iliad: Achilles is an Ass". Read it for the historical or cultural value, read it for the influence it had on future works, read it if you can in the original Greek to appreciate the structure of the poem, or even read parts of it to cure insomia ... but be realistic and just don't expect deep character development or a plot that stands up to more modern standards!