Tolstoy wrote across a long career — from the autobiographical trilogy he began in his twenties to the late novellas he produced after his religious conversion in the 1880s — and the reading experience shifts significantly across that career. The early work is social, psychological, and formal; the late work is stripped down, morally urgent, and sometimes didactic. The middle period (roughly 1863–1878) produced War and Peace and Anna Karenina, which are the novels most people mean when they talk about Tolstoy.
The best place to start is not the longest book, even though War and Peace is often cited as the first thing to read. The better entry point is the short fiction, specifically The Death of Ivan Ilyich (1886). This novella — about seventy pages — is one of the most concentrated and powerful works of fiction in any language. It follows a successful bureaucrat through his dying, which forces a confrontation with the question of whether his life has been well-lived. Tolstoy's method is visible here in its most efficient form: the attention to physical and psychological detail, the absence of sentimentality, the moral seriousness applied without moralizing. Reading this first gives you a clear sense of what Tolstoy does and why it matters, before committing to 1,400 pages. The Death of Ivan Ilyich is available in numerous editions; this Bantam Classics edition pairs it with other short works.
The second short work worth reading before the novels is Hadji Murat (1912, posthumously published), a short novel about a Chechen warrior during the Russian imperial wars in the Caucasus. Tolstoy wrote it late in life, drawing on his own military service in the Caucasus fifty years earlier. The book demonstrates his ability to inhabit a consciousness completely unlike his own — a Muslim warrior's view of both Russian imperial power and his own people — and the result is one of the most compressed and perfect pieces of long fiction he ever wrote. The Pevear and Volokhonsky translation is the standard choice.
After the short fiction, the natural progression is Anna Karenina before War and Peace. Anna Karenina (1878) is shorter — about 900 pages in most editions — and more tightly focused. It follows two parallel plots: Anna's affair with Vronsky and the destruction it brings, and Levin's search for the right way to live on his estate and in relation to the peasants who work it. The Levin plot is semi-autobiographical and is the part of the novel that people either find essential or nearly skip; most readers find it grows in retrospect, after the Anna plot has concluded. Anna herself is one of the great characters of world fiction: Tolstoy renders her with full sympathy and full understanding of how her situation was constructed by forces larger than her individual choices.
War and Peace (1869) comes next, and it is the novel that most readers who have worked up to it consider worth the investment. The reader who has arrived here via the short fiction and Anna Karenina will find the style familiar and the world already partially known. The novel follows the Bolkonsky, Rostov, and Bezukhov families through the Napoleonic Wars, from 1805 to 1812, and then traces their lives in the years after. Tolstoy's treatment of history — his argument that historical events are produced by millions of small decisions rather than by the intentions of great men — is embedded in the philosophical essays that interrupt the narrative. These essays are debated by critics and can be read quickly without losing the story. The Pevear and Volokhonsky translation is the standard for contemporary English readers.
Beyond the major works, the late religious essays — What Is Art? (1898), The Kingdom of God Is Within You (1894) — show a Tolstoy who has undergone the conversion his fiction was already pointing toward, and who is making arguments about art, nonviolence, and Christianity with the same directness and ferocity he brought to his fiction. These are not essential for most readers but are interesting for anyone who wants to understand the trajectory of his thought.
For readers who want to situate Tolstoy in relation to his contemporaries: Dostoevsky's The Brothers Karamazov is the obvious companion to any Tolstoy reading program. The two writers knew each other's work and held largely opposing philosophical positions. Tolstoy found Dostoevsky's chaos excessive; Dostoevsky found Tolstoy's moralism evasive. Reading them alongside each other — not simultaneously but in alternation — is one of the more rewarding experiences that nineteenth-century fiction offers. The literary fiction shelf at byallo carries The Brothers Karamazov.