Why e-mail can never replace the letter.

For literary critic F.O. Matthiessen and his artist lover Russell Cheney, who exchanged 3,000 letters over the 20 years from their first meeting in 1924 to Cheney's death in 1944, letters served as more than a means of communication—they became "tactile couriers" of the "lover's very DNA," as Mallon writes. Early on, the ardent idealist Matthiessen defined the relationship as "a marriage that demands nothing and gives everything." Yet, forced to live apart for much of the "marriage," and often in secret when together, the couple came to understand that it was letter-writing that allowed them to feel, as Cheney wrote, "I live with you all the time."

Just as compelling as Mallon's love stories are his accounts of several famous literary feuds, introduced with the observation that such rivalries "flourish between professional writers because the breed has difficulty resisting a display of weaponry it can fashion in its own verbal shop." Verbal chop shop, Mallon might well have said. In one of these, Vladimir Nabokov sparred with Edmund Wilson, surprisingly, over the Russian native's skill in translating Eugene Onegin. Wilson trashed Nabokov's translation as "full of flat writing, outlandish words, and awkward phrases"; Nabokov countered that Wilson's "Russian is primitive, and his knowledge of Russian literature gappy and grotesque." The ill will smoldered for most of a decade, with Wilson still stirring the embers in his late-life memoir Upstate, which Nabokov dismissed as "a flow of vulgar and fatuous invention."

Although nothing stings quite like being "flamed" over the e-waves, Mallon mourns the passing of the handwritten, or even hand-typed, letter—whether loving or vicious. "The glaze of impersonality over what pops up on that computer screen" spoils what once was the thrill of learning to "recognize the quirks of a person's typing, and typewriter" or a new friend's handwriting, which "has an intimacy and force that can never be matched." Never mind biographers; all of humanity will lose something incalculable as letters—those "tactile couriers"—vanish, to be replaced with "uniform pixels on a monitor."

Mallon quotes Ralph Waldo Emerson's definition of the letter as "a kind of picture of a voice." Handwriting, even if simply a signature scrawled at the bottom of a typed page, has always been part of that picture. Some of Mallon's correspondents, like WWI poet Wilfred Owen, considered letters an embodiment of the letter writer. "It seems wrong," Owen wrote to his mother from the front in January 1917, "that even your dear handwriting should come into such a Gehenna as this." It's hard to feel the same way about e-mail, IM, or a text message. No matter how you receive it, an electronic transmission, with "Forward" just a click away, can never seem as personal, private, or real as a handwritten letter meant for you alone.

"Please keep me alive with letters," wrote V.S. Naipaul in 1952 from Oxford to his sister Kamla in Trinidad. Nineteen and devastated by the rejection of his first novel, he was suffering from a loneliness so severe it resulted in a nervous breakdown. Maybe Naipaul wouldn't have felt so lonely if he and Kamla could have Skyped regularly or filed updates for each other and scads of "friends" on Facebook. Or would Vido have felt even worse? Is the virtual friend any more than a tease when genuine comfort is needed? Please keep me alive with your e-mails—? It's an appeal only Google could love.