In these books, Odysseus and Telemachus along with their friends slay all the suitors and punish those who have not been loyal, such as Melanthius, who is tortured and put to death. We also see the reunion of Penelope and Odysseus.
In view of the content, there can be a lot of exciting lessons. Let me suggest a few of them.
First, you can ask the students to go over Odysseus' strategy. Why did he do what he did and was it a good strategy? By asking this question, they will have to know all the suitor and how they died. This will make them know the content of book 22. Also you can have them come up with alternate strategies.
Second, you can ask your students to draw out a map of the battle scene. Some students who are more spatial might like this approach.
Third, you can ask your student to write a paper on the theme of identities. Deception and revelation of identity can be seen in both books. For instance, Penelope does not believe that it is really Odysseus. Also Athena is in disguise.