Jamie Groves has doubled his reading - up to more than 40 books a year - since he began downloading e-books on his Kindle.
Sandra Hines calls her Nook her "best Mother's Day present ever," after initially worrying, "It wouldn't feel like I was reading a real book."
Liz Jones used to buy a book every few months until she began reading on her iPod Touch. Now she's downloading a book a week.
All are converts to e-books - books read on handheld devices. Still a minority, their ranks are growing and transforming the definition of reading and books.
E-book sales make up 9 percent of the consumer book market. Through August, their sales are up 193 percent over a year ago, according to the Association of American Publishers.
Novelist Stephen King, who says he does nearly one-third of his own reading on an iPad or Kindle, sees e-books becoming 50 percent of the market "probably by 2013 and maybe by 2012." But he also warns: "Here's the thing - people tire of the new toys quickly."
For now, King, who experimented with writing a digital book, "Riding the Bullet," in 2000, when it had to be read on a computer, thinks people are reading more "because the screen now feels like home to them."
HarperCollins CEO Brian Murray reports "a sea change in the past few months" among new best-selling books: "On some books, the e-books are outselling the hardcovers."
It's a transformation, says Peter Osnos, founder of PublicAffairs Books, "in the same way that people moved from silent pictures to talking pictures to movie theaters to television to television-on-demand. We are adapting to the notion that we can choose where, when and how we read books."
An estimated 4 million U.S. homes have an e-book reader such as Amazon's Kindle or Barnes & Noble's Nook, according to Forrester Research, which predicts sales of more than 29 million devices by 2015.
In a Harris poll conducted in August, 8 percent say they have an e-reader; 12 percent are likely to buy one in the next six months. But 80 percent say they're not likely to do so.
Those results "ratify that using devices for something (reading) that doesn't require a device at all, and has worked perfectly well for centuries, may not be of obvious appeal to the bulk of readers," says Michael Cader, founder of Publishers Lunch, a digital newsletter.
Michael Norris, an analyst with Simba Information, a market research firm, also questions if a tipping point has been reached.
He sees "gradual, uninterrupted growth in e-books, but tipping point implies there will be something overnight which will instantly change the character of the publishing business. Thousands of new consumers are showing up in the e-book 'yes' column every day, but on the other hand, there are still over 120 million people who buy print books."
But that could change. A poll, released last month by Scholastic, the children's publisher, found that 57 percent of kids 9 to 17 said they're interested in reading e-books; one-third said they'd be more likely to read "more books for fun" with greater access to e-books.
Both Barnes & Noble and Borders have moved print books from the front of their stores to make room to display and demonstrate e-reading devices.
Most, but not all, e-books are cheaper ($9.99 to $16.99) than the print versions ($25 and up for hardcovers). And thousands of titles (from classics in the public domain to self-published) can be downloaded for free.
The cost of the device ranges from $99 for the most basic to $499 or more for Apple's iPad, which can be used for much more than reading books. But prices have dropped. The first Kindles cost $399 in 2007; the newest models start at $139.
Readers cite a variety of reasons for going digital, especially the ease of downloading e-books with a few clicks:
-In Huntington, Ind., Groves, 42, a county prosecutor, says that after his 9-year-old son found the first book in Rick Riordan's best-selling "Percy Jackson & The Olympians" series in his school library, it "was just too easy to order books 2 to 5 on the Kindle. Some nights we would finish one book, and it was nice to have the next book there in 60 seconds after downloading it."
But he doesn't share the Kindle as much with his daughter, 7, who favors picture books: "Dr. Seuss and 'Harold and the Purple Crayon' do not translate well into the black-and-white Kindle."
The only other downside, Groves says: "I purchase a lot more books, whereas I would previously trade with friends and family."
-In Lithonia, Ga., Hines, 49, a bookkeeper, says she has always been an avid reader: "Love opening a book, cracking the spine and having it in my hands."
But she's reading more than ever on her Nook, from classics such as "Dracula" to "sappy romances and some short stories of authors I've never heard of. It's easier carrying than a book, especially a hardcover, as they can get heavy."
In a compromise, she bought a case for her Nook "that opens, so it now feels like a book."
-In Roanoke, Va., Jones, 58, a legal secretary, says her iPod with a Kindle app is "so much easier to carry than a regular book."
After downloading a free e-book, Naomi Novik's "His Majesty's Dragon," Jones bought three more e-books in the alternate-reality series. Next on her reading list: free e-books of classics she never got to, including "Uncle Tom's Cabin."
-In Cary, N.C., Julie Powsner, 47, a saleswoman, says the Kindle app on her iPhone changed her reading habits, which include finally reading the "Twilight" series "to see what all the fuss was about."
She borrowed a copy of the first book, bought a print version of the second, and downloaded the last two books: "They were less expensive than the hard copy I purchased, which was a great benefit. I also didn't have to run to the store to get it."
-In Pearl River, N.Y., Kathy Miscioscio, 58, a marketing consultant, loves her local library's digital download center, which saves trips to and from the library.
She's reading more and faster because "e-books from the library cannot be renewed, and they are deactivated in 21 days."
-In Houston, Gregory Williams, 47, a hospital administrator, always has been an avid reader - three books a week - but is enjoying it more with his iPad.
And since he and his wife recently "downsized," he says, "the e-books have really helped with storage. All the books that I care to keep are in one little folder. It's awesome."
Others disagree. Julie Meier, 41, an office manager in Beaver Falls, Pa., says that part of her reading experience is the book itself: "pulling it from the shelf, inspecting the cover, letting it fall open to a random page."
After working at a computer all day, she wants "a book in my hand. Turning its pages is my way of knowing it's time to relax and slow down."
Other readers question if it's an either/or.
Miscioscio says she still listens to "vinyl records as well as music on an MP3 player," and that "exchanging good books with friends and browsing the book table at yard sales are activities many avid readers enjoy." But more and more, she's "turning on my Sony Reader rather than picking up a hard copy of a book."
Williams loves both bookstores and "the smell and feel of a new book. But I have noticed that when a new book is released, I immediately try to find out if the e-book is available."
Publishers face an uncertain world.
Grove/Atlantic's Morgan Entrekin says that "the change will not happen as fast as it has happened in the music business or even in the newspaper and magazine world." He sees a substantial market for physical books for at least another 20 to 30 years, "but eventually, 30, 40 or 50 years from now, e-books will be the predominant form."
King has mixed emotions about e-books.
At 63, the author appreciates being able to enlarge the print size, but cautions: "Let's just hope there won't be a terrorist EMP (electromagnetic pulse) that'll wipe them all out.
"They are ephemeral. In a very real sense, not books at all. Of course, books themselves are hardly indestructible: The Germans burned plenty. Not to mention the fundamentalists, who have cheerfully burned some of my own."
Explore further: Amazon unveils new Fire tablets and Kindle e-readers