Our own Robert Bly has just been awarded the Poetry Society of America's highest honor, the Frost Medal, for his "distinguished lifetime achievement in poetry." His close friend, Swedish poet Tomas Tranströmer, won the Nobel Prize in Literature in 2011. Publication of the correspondence of these two literary lions is a notable event, and long overdue. Thanks is owed to Graywolf Press for this delectable book, consisting of nearly 300 letters from three decades, and ably edited by poet Thomas R. Smith.

Bly, as editor of the feisty magazine The Fifties (later The Sixties and The Seventies), was leading the charge for a "new poetry," freed from old constraints and based on the intuitive image as a way of linking the inner and the outer worlds. The first step for young American poets, he said, was to learn from reading poetry in translation and by translating it oneself. Bly practiced as he preached, starting the Sixties Press in order to publish his own and others' translations from various languages. At the same time, his landmark first book of poetry, "Silence in the Snowy Fields," took the literary world by storm.

Then, in 1964, Tranströmer and Bly connected, finding "an instant kind of communion," and began at once to translate and learn from each other. Although theirs was a mutually beneficial relationship (conducted by mail and face-to-face), Tranströmer persistently deferred to Bly as "master." Bly was the first to translate a book of Tranströmer's into English. Many other translators followed suit.

Taking us behind the scenes, the letters gathered here reveal much about this great pair: their intimate and enduring friendship; the joys and sorrows of their personal and family lives; the nature of their respective societies and cultures; upheavals in national and world politics; their dreams and psychological insights; their buoyant good humor; literary news and gossip; and, most important, the processes of their own work and their literary collaboration. While both writers remark on their apparent occasional telepathy, translating did not happen by osmosis, but remained very hard work. Certainly part of the fascination of these letters for American readers is that Bly's public persona, his reputation for bombast and controversy, is hard to find. He and the more introverted Tranströmer both appear as their authentic private selves — generous, humble, vulnerable and self-deprecating to a fault.

As technological change presses ahead — with tweets, texting, Facebook comments and e-mail now standard means of communication — letter writing is a dying art, seen as quaint at best. Whether or not one is grateful for the speed and ease of electronic messaging, this marvelous collection, both entertaining and edifying, provides one opportunity to measure what has been lost.

Mark Gustafson, author of "The Odin House Harvest," is writing Robert Bly's biography. He lives in Minneapolis.