See her journals, Memories of a Hostess (ed. by M. A. De Wolfe Howe, 1922).
In 1839, he joined William Ticknor and became junior partner in the publishing and bookselling firm known after 1846 as Ticknor and Fields, and after 1868 as Fields, Osgood & Company.
He was the publisher of the leading contemporary American writers, with whom he was on terms of close personal friendship. He was also the American publisher of some of the best-known British writers of his time, some of whom he also knew intimately. The first collected edition of Thomas De Quincey's works (20 vols., 1850-1855) was published by his firm. As a publisher, he was characterized by a somewhat rare combination of keen business acumen and sound, discriminating literary taste, and as a man he was known for his geniality and charm of manner. Acknowledging Fields's influence in the literary scene, Nathaniel Parker Willis once wrote to him, "Your press is the announcing-room of the country's Court of Poetry.
In 1862–1870, as the successor of James Russell Lowell, he edited The Atlantic Monthly. In 1871, Fields retired from business and from his editorial duties, and devoted himself to lecturing and writing. He also edited, with Edwin P. Whipple, A Family Library of British Poetry (1878).
His chief works were the collection of sketches and essays entitled Underbrush (1877) and the chapters of reminiscence composing Yesterdays with Authors (1871), in which he recorded his personal friendship with William Wordsworth, William Makepeace Thackeray, Charles Dickens, Nathaniel Hawthorne, Herman Melville and others. He died in Boston on April 24, 1881.
In addition to his work as a publisher and essayist, Fields wrote poetry. A number of his works are collected in his book Ballads and Verses published in 1880. This volume contains the poem Ballad of the Tempest, which includes the famous lines:
His second wife, Annie Adams Fields, whom he married in 1854, was also an author. She wrote his biography Memoir of James T. Fields, by his Wife (Boston, 1881), and Authors and Friends (Boston, 1896), which also makes mention of him.
Fields was known in his lifetime as one of the most successful and shrewd book promoters, working at a time when bribery was typical in the publishing culture. Hawthorne said he owed his success as a writer to him: After Fields's death, his friend Henry Wadsworth Longfellow wrote a poem called "Auf Wiedersehen" dedicated to him. Fields, along with Longfellow, is featured in Matthew Pearl's novel The Dante Club. Fields is also mentioned in the 1994 film version of Little Women.