I love The Illiad only a little bit less than The Odyssey, the other epic poem attributed to Homer. Together the two works are considered among the oldest surviving works of Western literature, dating to probably the eighth century BCE, and are certainly among the most influential. The Illiad deals with just a few weeks in the last year of the decade-long Trojan War. As the opening lines state, it deals with how the quarrel between the Greek's great hero Achilles and their leader Agamemnon "caused the Akhaians loss on bitter loss and crowded brave souls into the undergloom."
So, essentially, this is a war story. One close to three thousand years old with a mindset very alien to ours. One where unending glory was seen as a great good over personal survival or family. One where all felt that their ends were fated. And one with curiously human, or at least petty, gods. Some see the work as jingoistic, even pro-war, and I suppose it can be read that way, but what struck me was the compassion with which Homer wrote of both sides. We certainly care for the Trojan Hector as much as or more (in my case much more) than for the sulky and explosive Achilles. For the Trojan King Priam as much or more (in my case much more) than King Agamemnon. Homer certainly doesn't obscure the pity, the waste, and the grief war brings. And there are plenty of scenes in the work that I found unforgettable: The humorous scene where Aphrodite is wounded and driven from the field. The moving scene between Hector and his wife and child. The grief Helen feels in losing a friend. The confrontation between Priam and Achilles.
This is one work where translations make a huge difference. Keats poem "On Chapman's Homer" is all about how a translation opened his eyes to "realms of gold" in The Illiad he had not appreciated before. I was forced to read Homer in high school (I suspect the Lattimore translation) and hated it as boring and tedious. Maturity might have helped change how I felt on reread--but I had my own "Keats Experience" when I discovered Robert Fitzgerald's translation. I've never read the Fagles translation some reviewers are recommending, but you might want to look up various translations to see which one speaks to you before embarking on a full read.