This chapter summarizes the books, but it also gives us the backstory for the first time. Of the Rings of Power and the Third Age is the chapter for you if you've ever wondered who Sauron was, how he got so powerful, or why he did not have a physical form. It begins to get a bit easier to listen to over time. Stick with it.
The concluding section of the book, comprising about 20 pages, describes the events that take place in Middle-earth during the Second and Third Ages. In the Second Age, Sauron re-emerged in Middle-earth. The Rings of Power were forged by Elves led by Celebrimbor, but Sauron secretly forged One Ring to control the others. War broke out between the peoples of Middle-earth and Sauron, culminating in the War of the Last Alliance, in which Elves led by Gil-galad and the remaining Númenóreans led by Elendil united to defeat Sauron, bringing the Second Age to an end.
The Third Age began with the claiming of the One Ring by Isildur after Sauron's overthrow. Isildur was ambushed by orcs and killed at the Gladden Fields shortly afterwards, and the One Ring was lost in the River Anduin. The section gives a brief overview of the events leading up to and taking place in The Lord of the Rings, including the waning of Gondor, the re-emergence of Sauron, the White Council, Saruman's treachery, and Sauron's final destruction along with the One Ring, which ends the Third Age.