The three major themes are the corrupting influence of power, the ultimate struggle between good and evil, and the selfless sacrifice for the greater good.
The minor themes are those of Fate, diversity, responsibility, faithfulness, and obedience.
Th mood is definitely imaginative, fantastic, an adventurous. Middle-earth is a new world where the rules and norms are vivid and dynamic. There is some awe, some wonder. There is suspense, danger, and restoration. As with any epic, The Lord of the Rings encompasses a gamut of emotional tones and moods. In the end, the reader response is as vivid and changing as the Middle-earth landscape.
J.R.R. Tolkien, who was born in 1892 in South Africa, grew up in Birmingham, England with his mother after the early death of his father. Tolkien attended school at the prestigious Oxford University until he left to fight in World War I as a member of the Lancashire Fusiliers. In 1919, when the war was over, he returned to school and his wife, whom he had married during the war.
Tolkien's intellectual career began when he was selected to assist in the compilation of the Oxford English Dictionary. After that he taught and accepted academic fellowships until completing The Hobbit in 1938. His first novel was an immediate success with both children (for whom it was written) and adults, for whom it was an imaginative tour de force. The Lord of the Rings followed the Hobbit in 1954. Tolkien died in 1973 before completing a massive literary undertaking that included the complete history of Middle-earth, known as The Simarillion. Tolkien still maintains his status as one of the most-loved writers of "fantasy" literature today, and his popularity only grows with each new generation of fans.
Tolkien and C.S. Lewis were members of a literary circle called "The Inklings," to whom fantasy and religion were important compensations for the inadequacies of contemporary life. After Tolkien pointed out the mythical qualities in the death of Christ, Lewis embraced Christianity.
Beowulf, written after the introduction of Christianity to England, describes a pagan world populated by evil forces personified in dragons and monsters, but includes no mention of a Supreme Being or a Christian God. Tolkien interprets its theme as man at war with the hostile world. The Lord of the Rings is set in a world reminiscent of these times, only with covert traces of Christianity and/or a divine presence.