THE SELECTED LETTERS OF WILLA CATHER. Edited by Andrew Jewell and Janis Stout. Knopf. 715 pages. $37.50.

‘I have been running away from myself all my life ... and have been happiest when I was running fastest. Those last three winters of my mother’s life held me close to myself and to the beginnings of things, and it was like being held against things too sad to live with,” writes Willa Cather in 1933.

Cather’s was a restless and philosophically mobile mind, and “The Letters of Willa Cather” is a restless and philosophically mobile book.

From the earliest letter, written when she was 14, it’s clear that Cather’s mind will be the treat of the volume. She carries a head stocked with ideals, some of them pitting the past against the present and East against West.

As much as she loved the plains and prairie of Nebraska — and she made her first fame with three show-stopping novels set there — Cather was itching to run far and fast away from the provinces.

These letters tell a great story of self-possession in the vital, direct language that is Cather’s hallmark. What her editors call “the tang of Cather’s character” is irresistible.

So why the 66-year embargo on quoting from the roughly 3,000 existing letters?

Their publication now in “The Selected Letters” is a grand literary event, a dream come true for Cather fans.

Andrew Jewell and Janis Stout are expert editors who serve Cather well with a gorgeous selection of 566 letters and editorial commentary that’s just right: useful and informative without being pesky and obtrusive.

They make it clear that they are flouting Cather’s will: “We fully realize that in producing this book ... we are defying Willa Cather’s stated preference that her letters remain hidden from the public eye.”

They also put to bed speculation that the letters hide dark secrets, particularly revelations about her sexuality.

Cather, it seems sensible to conclude, was not in the closet. Her private life was private, but she was not ashamed to live openly for 39 years with her partner, Edith Lewis.

Myths that she systematically burned or asked others to burn the correspondence also don’t hold up. Jewell and Stout suggest that Cather, as a “skillful self-marketer,” was interested in shaping the public’s access to herself and her work: “Her goal was to create a persona that practically disappeared behind the work.”

One of the pleasures of Cather’s letters is in how much delight she took in every detail of the writing and making of books. No better guide to her work, its origins and moods, exists.

When she is out of college and doing magazine and newspaper work in Pittsburgh, the young Cather already knows that writing “takes all the ennui out of life.” After a long run-up, with an important stint as managing editor at McClure’s Magazine, Cather was finally able to devote herself full time to fiction at 38.

Whether she’s gloating about the bloody murder in “O Pioneers” (“I spent three mortal days a-killing them!”) or reminiscing about the old friends she brings to life in “My Antonia” (“The older one grows, the dearer and the clearer one’s early impressions somehow become.”), Cather is zesty and intimate when she writes about her books.

“A Lost Lady” is “a little lawless un-machine made thing.” Professor St. Peter (of “The Professor’s House”) “has just gone and bought me a grand mink coat.” The writing of “Death Comes for the Archbishop” was “the most unalloyed pleasure of my life.”

Late in her life, Cather identified the source of her literary power in a letter to her brother, Roscoe: “As for me, I have cared too much about people and places — cared too hard. It made me as a writer, but it will break me in the end.”

Cather was a cosmopolitan woman, and she exchanged letters with many of the greats of her time, among them F. Scott Fitzgerald, Langston Hughes and Robert Frost.

But her most revealing letters are those that showcase her capacity to care over the long haul, especially for family and friends from childhood and college. To these dearest friends, Cather discloses both the beauty and the cost of living. As a young person, she wrote, “There is no place in my scheme of life for the unlucky.”

Older, she knows that luck is often beside the point. It “rains death,” and each year brings new “vanishings.” She records her own “dents and scars.” On every subject she is heartfelt and candid; the letters fizz with the nearest emotion.

Cather throws herself on the page in a loose, modern way. She lived the 20th-century American story of accelerating speed and distance, burning up track on an east-west axis.

If occasionally in her last years she suggests that some distances are too far to travel, she also shows that it is possible to mourn a lost culture while retaining a precise love for what’s left behind.

Reviewer Catherine Holmes teaches English at the College of Charleston.