The Lord of the Rings is an epic of the fate of the world of Middle Earth, a classic tale of good vs. evil. Middle Earth is populated by four main races: Elves, Dwarves, Men, and an evil race of orcs, goblins, and wraiths.
The story begins with the creation of the Rings of Power. The most powerful of each race (including the evil races) created magic rings which held the power to govern its members. The Lord of the evil races, Sauron, created a "master" ring that held power over each of the others and, as a result, all races of Middle Earth.
Sauron proceeds to establish and expand an empire marked by war, fire, and darkness. The races of elves and men unite to defeat the armies of Sauron and cut off the hand upon which he wore the One Ring. They physical form of Sauron dissipates, but the Ring remains. To destroy evil forever, the Ring had to have been cast into the volcanic fires of Mount Doom, where it was forged.
But the very evil that lives in the Ring influences King Isildur to keep it for himself. This proves fatal as Isildur is later killed over the Ring, but during the attack the Ring itself is lost to the bottom of a lake.
After many years, the evil has laid dormant long enough and Sauron seeks to retake physical form and his place as Lord of all Middle Earth. He sends forth his minions to bring him the Ring, which has been found, from a hobbit living in the Shire. The three book series that is The Lord of the Rings begins with a small band that includes and elf, dwarf, men, and hobbits and their quest to destroy the Ring while they are actively hunted my all evil.
The climax of the story would be the Battle of Minas Tirith and Frodo and Sam's final approach to Mount Doom. It is an epic battle between a monstrous army of evil and a terribly outnumbered collection of men and elves from different parts of Middle Earth, while at the same time two hobbits have the Ring in the very center of the evil lordship of Mordor and must slip past thousands of orcs to reach Mount Doom.
The Ring is destroyed and with it all evil. A king returns to the throne of men for the first time in thousands of years and a new golden age dawns for Middle Earth. The hobbits return to the Shire heroes and a select group finally sails off to a land of immortality.