Compare and contrast Homer's Iliad Book 9 and Book 24 in reference to theme, plot development, and character importance.
In Book 9 of The Iliad, Achilles is still sulking in his tent, fuming over the disrespect shown to him by Agamemnon. Agamemnon had handed Achilles' sex slave back to her father to appease the wrath of the gods, and Achilles, thinking only of himself as usual, was not best pleased. Since then, the Achaeans have tried everything they can think of to coax Achilles out of his tent, but all to no avail.
The war's not going very well for them, and they need their best warrior out there in the thick of battle. But Achilles doesn't budge an inch. Not even a generous bribe of treasure is enough to move him. It seems for all the world as if the Achaeans are on the brink of giving up and going home. Diomedes may say that the Greeks can do without him, but deep down, everyone knows that just isn't true.
By the time we reach Book 24, Achilles has not just returned to battle—to avenge the death of his bosom pal, Patroclus—he's also changed the whole course of the war with his crucial intervention. Killing Hector has severely weakened the Trojans, who are in turmoil without their leader. When Hector's father, King Priam, approaches the Achaean camp to retrieve his son's broken corpse, Achilles puts aside his legendary stubbornness and agrees to Priam's heartfelt request. He can see shades of his father Peleus in Priam. Not only that, but he can empathize with Priam's grief as it so clearly matches his own over Patroclus.
If the theme of Book 9 was stubbornness and its dangers, the theme in Book 24 is the importance of empathy. Hector's death has clearly affected his loved ones deeply, and they lament his loss with great intensity. As for Achilles, his character appears to have undergone a considerable change from Book 9. He may still be a proud, fearsome warrior, but for the first time he seems to have an inkling of the damage that war can inflict on people. Through the death of his closest friend in battle and the heartfelt entreaties of Priam, he's developed empathy, which allows the Trojans at long last to give noble Hector, breaker of horses, a decent, dignified burial.
In both books, Achilles is unforgiving in his anger, one of the themes. He will not relent in either book. The difference is that in Book 9 he will not forgive Agamemnon for taking Briseis, even though Agamemnon is willing to give her back and pay him back handsomely. This shows us that Achilles is stubborn and too proud to forgive Agamemnon.
In Book 24 we see a different side of Achilles. The book begins with him dragging Hector's body behind his chariot over and over again. He wants his revenge, another theme, just like he wanted it against Agamemnon in Book 9, and once again he is stubborn and won't give up Hector's body. The difference then is when Priam appears and begs him for his son back. We see a difference in Achilles here. He gives Priam his son's body. He gives in because he is reminded of his own father when talking with Priam. This is a different Achilles than the one we saw in Book 9. Together the men cry over the loss of humanity altogether, not just for their loved ones. Together they recognize mortality for what it is, which is another theme.
Both books appear to be an end of something big in plot development. Book 9 sounds like it might be the end of fighting and war for the Achaians, as they may be heading back home the next morning. The last book ends rather abruptly with the funeral for Hector. The fighting is no more, and Achilles, the important main character of the epic, has transformed.