Four years ago, I resolved to get more seriously into shape. This least literary of decisions soon opened the way to the greatest revolution in my reading habits since I discovered books without pictures. The new regimen demanded many more hours on treadmills and bicycles, hiking up mountains and walking dogs. To make the exercise time more endurable, I bought my first iPod and my first digital audio-book, I had listened to recorded books for years, but only in the car, and I hated the ride-delaying or life-threatening fussing with cassettes and disks. The iPod promised to put an end to all that.

As it did so, it altered the habits of a lifetime. Through my adult life I had always read a single book at a time. Now I was reading two, one on paper, one in the ear. No longer did I tuck a bound volume under my arm whenever I left home or office. I just dropped my iPod in my pocket and could go anywhere without the haunting fear that I might be stranded in line somewhere without anything to read.

But is “reading” even the right word? Listening is a very different activity from engaging with a book on the printed page, as I discovered while struggling through the three volumes of Shelby Foote’s history of the Civil War. As Foote’s prose flowed past me, I was certainly able to appreciate the majestic wit of this great American narrative. Yet I absorbed much less of it than I wished.

Had I read the book on the page, I would have done what I usually do when immersed in a dense work of history. I would have flipped to the index every time a character reappeared to remind myself of all his previous history. I would have surrounded myself with maps and atlases to connect history with geography. I would have stacked up other books on similar subjects, and checked Foote’s version against other authorities who disagreed with his conclusions or emphases. Had I read The Civil War between covers, I would have examined the endnotes and scribbled little reminders to myself about things that puzzled me. Listening while racing on an elliptical trainer, I could be only a passive auditor.

I had a marvelous English teacher in my last year of high school. On the day we started studying Beowulf, she led the class to the gym, had us lie on mats, switched off the lights — and then, standing in a corner of the echoing room, began to chant the Anglo-Saxon verses. She wanted us to experience the poem as it was first experienced: aurally, echoingly, in the dark. As she demonstrated, the transition from primitive to modern literature was a transition from ear to eye. The journey backward from eye to ear provided by the audio-book leads us from the more sophisticated to the more fundamental: from information to narrative, from symbolism to story, from nonfiction to fiction and then within fiction from the more demanding to the more simple. Henry James doesn’t work on the iPod; H. Rider Haggard does.

One listens with less than perfect concentration: while running or hiking, while shopping for dinner. It’s done far from the study where atlases and dictionaries live, away from a computer terminal where odd facts can be checked (so that’s what a Dahlgren gun is).

Reading is a supremely intimate dual relationship: writer and reader. Listening is three-way: writer, performer, and listener. A bad reader can spoil a good book and wreck a weak one. (I still wince at an especially stagey reading of Elizabeth Gaskell’s North and South by an actor who sounded like a basso profundo Dudley Do-Right.) On the other hand, a fine reader can imbue a quite ordinary book with unsuspected depths. George Guidall breathes an air of sadness and loss into Alan Furst’s spy novels I’m not sure Furst ever placed there. Sam Dastor does a version of Rudyard Kipling’s Kim in which he manages a variety of accents that would impress Henry Higgins: Bengali Hindu, Punjabi Muslim, and a range of English accents varying precisely correctly according to the class and education of the characters.

Yet however successful or not the performer may be, the most important thing about him is: he or she is always there. The experience of reading — the most direct mind-to-mind experience one human being can have with another — is mediated, refracted, interpreted. When this interpretation differs from one’s own of some work known and loved in print, the effect is very jarring.

A couple of my own books have been recorded. I can hardly stand to listen to them. One, the most personal, is read by an actor who sounds remarkably like David McCullough. I don’t. To hear my own stories and jokes re-accented in the flat, nasal accents of the American prairies rather than my own blend of Eastern Europe and southern Ontario was like seeing another man walking alongside your wife. With a book one has not written oneself, the effect is less jarring, but more insidious and dangerous when applied to an unfamiliar text. The reader’s interpretation asserts and inserts itself, stifling one’s own understanding before that understanding can ever take form.

The world of printed literature is vast, unfolding, practically limitless. The literary listener’s library is surprisingly small and oppressively provincial. It’s a world in which the novels of Thomas Mann and Robert Musil are unknown; where Balzac is the author of a couple of titles and Stendhal of only one; where Proust is available only in enraging abridgment and Giuseppe di Lampedusa is not available at all. Even English and American authors are hit and miss. Evelyn Waugh’s World War II trilogy does not exist; ditto all of Walter Scott except Ivanhoe and Rob Roy, ditto everything of Thackeray other than Vanity Fair, ditto all of John dos Passos.

Thrillers? Chick lit? Self-help? Fantasy fiction about elves and galactic warriors? All superabundantly present: 50,000 of them in total and growing every day. And fair enough. People want this stuff. But for the apparently tiny minority that might want something else, trying to find something to listen to becomes after a very short time like trying to find something to read at an airport newspaper counter with a small row of paperbacks next to the car magazines.

On the other hand, maybe there is a bright side to the narrowness of the audio library. It’s been said that we buy books in part to assure ourselves that we still have remaining to us the time to read them. With books on paper, there is always a helpful uncertainty about our commitment. Not so with audio-books. We know to the second how long they will last, and we can make a reasonably informed guess about precisely how many we will read in the coming years. The actuarial tables can then calculate how many will we read before we ourselves are finished. The illusion of unbounded time for unbounded reading vanishes.

Maybe the biggest surprise of the audio-book is the revolution this format can work in one’s own taste. I suffered through Thomas Hardy in high school and university and never returned to him. All those damn sheep-shearing scenes. Read aloud, the sheep shearing suddenly seemed almost exciting — and the books more than fulfilled the advertising of my professors, as moving descriptions of a way of life vanishing before the author’s eyes.

The Mayor of Casterbridge opens like a bomb exploding; the tragedy in The Return of the Native hurtles overwhelmingly down upon the ear; and the happy ending of Far From the Madding Crowd is one of the few in literature that seems thoroughly earned and convincing.

To listen to Dickens in order of publication is to experience the eruption of some mighty mountain chain of talent, the entertaining but flawed early works rising and overtopping into the gigantic works of imagination of the mature writer. The comic characters talking in the ear as you walk, bicycle, and run become more real than most of the people you speak to in your ordinary day, and you find yourself staggered again and again by the question: How did one man create all this?

But then there are the writers to whom the ear does no favors. The eye edits, omitting redundant passages, racing through boring bits, leaping over excessively poetic language and tedious philosophical speculation. The ear has to soldier its way through them all.

I thought I loved Anthony Trollope and Robert Penn Warren. Now I’m not so sure. When every word gets equal weight, Trollope suddenly seems sloppy, and Warren’s attempt to fuse the literary influences of T.S. Eliot and Raymond Chandler suddenly seems exhausting.

The audio-book has put an end to my nearly 40-year habit of reading while walking — conduct that was probably going to get me killed one of these days. It fills time that might otherwise have been wasted with pleasure and meaning. On the other hand, it has also probably worsened my tendency to inwardness and isolation. When I tidy the kitchen after dinner, I do it with ear buds in my ears, which means that “huh?” becomes my new first answer to any question my wife or children ask me.

I know it’s odd to walk up a mountain path listening to the story of a Victorian love affair rather than the whistle of the wind, and probably a person with greater inner resources would not feel the need for the company of writers at all times and places. And yet, since I do need that company, I am grateful to be able to claim it in even in the line at the Department of Motor Vehicles.

Listening is a three-way relationship: writer, performer, and listener. A bad reader can spoil a good book and wreck a weak one. A fine reader can imbue a quite ordinary book with unsuspected depths.

There are the writers to whom the ear does no favors. The eve edits, omitting redundant passages, racing through boring bits, leaping over excessively poetic language. The ear has to soldier its way through all of them.