'The Hobbit' turns 75 this week, an occasion that will cause many to fondly reflect on their childhood memories of the adventures of Bilbo Baggins. "The Hobbit" remains widely respected as a children's book, but too often it is overlooked by adults. It tends to remain locked into the category of "juvenile literature," and even serious fans of J.R.R. Tolkien sometimes neglect it when they grow up and move on to "The Lord of the Rings" and "The Silmarillion." But Tolkien's first published novel is a much more sophisticated book than it often gets credit for, and it richly rewards adult rereading.

"The Hobbit" turns 75 today, an occasion likely to cause many thousands of people to reflect with fondness on their childhood memories of the adventures of Bilbo Baggins. Christopher Farley has details on Lunch Break.

Tolkien's characters have a fascinating depth, and none more so than Bilbo himself, who presents a striking psychological study. Bilbo is caught between conflicting impulses: his love of comfort and safe, familiar surroundings and his latent desire for adventure, for the marvelous and unknown world that he has encountered only in stories. Tolkien associates these rival tendencies with the two families from which Bilbo springs: the staid Bagginses and the fabulous Tooks.

Bilbo's Tookishness first rises up within him when he hears the dwarves sing their song of gold and dragons, and he soon finds himself unexpectedly volunteering to accompany the dwarves on the journey to recover their lost treasure. But Bilbo's story is much more than just the development of an unlikely and reluctant hero. His Baggins side, which looks at times like mere parochialism and timidity, doesn't fade and disappear as he adjusts to the world of adventure. Instead, Tolkien maintains the balance between these two aspects of Bilbo's character, showing how they mature into courage and wisdom.

Bilbo's culminating act of heroism isn't a bold rescue or the slaying of a monster but his attempt to prevent a war between allies through an act of great self-sacrifice, and at the cost of being thought a traitor by his friends. It draws on the daring of his Took side and the common sense of his Baggins side, which complement and enhance each other.

'The Hobbit: An Unexpected Journey' comes out in December. Warner Bros. Pictures

One of the most consistently underappreciated elements of "The Hobbit" is Tolkien's use of poetry and song throughout the book. Most readers skim over the poems or even skip them outright, but those who do miss out on some of Tolkien's most compelling literary moments. The songs in "The Hobbit" aren't merely verses embedded in the story; they are carefully designed to capture the voices and illustrate the attitudes of their singers.

The simple chant of the goblins when they first capture Bilbo and the dwarves, for instance, gives readers stark insight into their outlook on life in the first few short lines: "Clap! Snap! the black crack! / Grip, grab! Pinch, nab!" The harsh, explosive consonants and the action-focused, verb-heavy monosyllables instantly immerse us in the hard, violent world of the goblins, who take pleasure in acts of cruelty. The dwarves' song in Bilbo's kitchen—in which they cheerfully threaten to "Chip the glasses and crack the plates!"—sounds similar, but the relative complexity of the dwarves' phrasing and poetic lines demonstrate their comparative mildness. Readers easily grasp the domesticity of their (merely humorous) threats. The wood-elves also sing a monosyllabic song as they watch their barrels roll into the river, but their soft liquid consonants ("roll-roll-rolling down the hole!") and their enjoyment of amusing sounds ("Heave ho! Splash plump!") show that their simple pleasures are as innocent as the goblins' are cruel. Tolkien's poetry enriches and complements not only the plot of the story but the development of his fictional world.

"The Hobbit" is a brilliantly constructed story, unfolding themes that remain all too relevant to the modern world: the nature of evil, the significance of human choice, the corrupting power of greed and the ease with which good people can be drawn into destructive conflict. There is plenty there to entertain children—and even more to draw in adults.

—Mr. Olsen is an assistant professor of English at Washington College, founder of the Mythgard Institute and author of "Exploring J.R.R. Tolkien's 'The Hobbit.' "