The legend preceded her: the Russian-German beauty, not yet 21, who so infatuated Friedrich Nietzsche that he proposed marriage to her before bitterly denouncing her and admonishing his followers to “not forget the whip” in their relations with women. Louise von Salomé was born in 1861 in St. Petersburg into a German-Baltic family and, like her contemporary Alma Mahler, made a career of subjugating talented men with her sexuality, intelligence and steely independence. Her conquests included her pastor in Russia (he 42, she 17), Nietzsche and Nietzsche’s philosopher friend Paul Rée (with whom she lived in Berlin on the condition they not have sex), the gifted linguist and Armenian-German aristocrat Friedrich Carl Andreas (whom she married on the same condition) and, in platonically collegial fashion, Freud.

But Rilke was her biggest coup. She met the unknown German-speaking poet from Prague in 1897 when he was 21 and she, fifteen years his senior, already a well-known essayist and cultural personality. He began showering her with effusive love letters and precious verse that she initially ignored before finally “succumbing” and then quickly dominating him. They became lovers and constant companions for the next few years in a typically countercultural, proto-hippie, turn-of-the-century way, walking barefoot through the woods, eating fruit paps with yogurt, studying religion as an artistic experience and art as a form of religion. Tolstoy, whom they traveled to Russia to meet, was their patron saint.

Though Salomé was a formidable intellectual, novelist and practicing psychoanalyst, her most lasting contribution to European culture may well be her role as poetic midwife to the greatest German lyric poet since Hölderlin. It was she who recognized the makings of genius in the bundle of neuroses, preciosity and über-feeling that made up the young “René Rilke,” helping him through various personal crises to accept the “Other” in his psyche without which he never would have forged the Modernist style of the New Poems, his novel The Notebooks of Malte Laurids Brigge or his poetic masterpiece, the Duino Elegies. Soon after their first encounter she starts calling him by the “fine, German name” Rainer; teaches him to read Tolstoy and Pushkin in the original Russian; opens for him the doors to wealthy patrons, aristocrats and artists; and after their affair is over, continues to advise him about his love relationships, his diet, his choice of doctors, his writing. Denied as a lover, he grovels for a meeting, a word of advice, any sign of the woman he still sees as “the single bridge to [his] future.” She responds by turning herself into the recipient of his increasingly disturbing depressions and hallucinatory states. “Write about how you feel and what’s tormenting you,” she counsels him in 1903, a full decade before studying psychoanalysis, “write it out of your system.” She more than anyone is the person he wrote for, his first and only great love, his ideal reader. The printed dedication to his verse collection The Book of Hours (1905) reads simply “laid in the hands of Lou for all time.”

The correspondence charts this mesmerizing act of poetic midwifery over three decades, from the Munich apartment of Jakob Wassermann, where they met, to Rilke’s death in a Swiss clinic in December 1926. While Salomé lives a celibate life with her husband and beloved dog in Göttingen, Rilke travels compulsively throughout much of Western Europe, an itinerant monk or self-described “hunted animal” who goes from hotel room to rented apartment to patron’s castle, always looking for that perfectly quiet, healthy and beautiful space in which he will finally be able to write as he wishes. Impeccably translated by Edward Snow and Michael Winkler, these letters provide a snapshot of European culture in the enormously fertile periods before and after World War I. Their circle of acquaintances is a veritable “Who’s Who” of high society and artistic personalities, their reading matter eclectic and demanding: Baudelaire, Kierkegaard, Ellen Key, Georg Brandes (“more an amusement park than a human being”), Otto Weininger, Spengler, Proust, Valéry; psychoanalysis and spiritistic mediums; Italian Renaissance studies and contemporary artist colonies. For all their self-absorbed focus on their work and bodily ailments, Rilke and Salomé keep each other apprised of what is innovative in high European culture (all of it helpfully glossed in well over 300 footnotes that by themselves are worth the price of the book).

The real interest of these letters lies, however, in the intimate portrait they give of a poet struggling to accomplish what he felt was his Auftrag, or “mission.” Not every reader will appreciate the writers’ pathos-laden and very German “high style.” Much is insufferably long, self-indulgent or just plain obscure, and might have benefited from a pair of judicious editorial shears. On the other hand, without the full record of these exchanges, one cannot fully grasp the nature of this culture’s relation to art or the intensity of Rilke’s poetic ambition–ambition that left him little time to be with his daughter but required him to see the latest exhibition of paintings or to write a thank-you note to an aristocratic acquaintance. Throughout, his work remains the focus. “One must always work,” Rodin admonished his young German secretary, and Rilke complied by writing poem after poem until he achieved the sculptural plasticity and objectivity he so admired in the French artist. In the process he became so absorbed by his art that his distant beloved had to beseech the famous poet for attention.

Salomé remains a cipher in these letters. She analyzes with increasingly Freudian rigor Rilke’s childhood fears and artistic crises, yet she offers not a single explanation (or complaint) about her thirty-year marriage to a man with whom she refused to have sex. Rilke’s life is laid out on a dissecting table, hers is kept veiled in the high-minded, self-effacing role of Muse. They last see each other in 1919, but their letters reach an emotional high point with his breakthrough of 1922, when he finishes the Elegies and composes the Sonnets to Orpheus in two miraculous weeks, which they both experience as the culmination of their relationship. His Auftrag accomplished, he acquiesces to the sickness that had been knocking at his body all his life. In the month leading up to his death, he refuses to let any visitors see him, not even his wife or his last lover; but “Lou must know everything,” he tells his caretaker. All of the five letters she wrote to him the week before he died are lost; his last letter ends: “There is something malign blowing through the end of the year, something menacing,” and then (in Russian), “farewell, my love, Y. Rainer.”