'I don't go anywhere without my boyfriend Kindle," says Jen Pechet, a self-professed addict to Amazon's popular e-book reader.

She takes it to bed, the dentist's chair, the sidelines of her sons' baseball and lacrosse games, the grocery store parking lot, and the carpool line at school.

Pechet was a serious reader before, but the Kindle has upped the ante, luring her to read as many as three books in a single day. Since getting the device in June, she's lined the shelves of her digital library with more than 500 books (that's an average of 41 a month!).

"Just last week I was waiting at the doctor's office. I finished reading an Elizabeth George mystery and wanted more, so I fired up the Kindle store," she says.

With more than 11 million total expected to be sold by the end of this year, e-readers, which retail for $150 to $500, are increasingly found in mainstream hands - not just those of gadget hounds.

Yet whether they have a Kindle, a Sony Reader, a Nook, or an iPad (or all four), users are discovering how e-readers earn high praise for some features but elicit scorn for others.

It's good, they say, for access and portability. Smaller than a paperback, e-readers can hold up to 1,500 books at a time, and technophiles love features such as integrated dictionaries and highlighting and note-taking capabilities.

But what about such tactile pleasures as flipping pages back and forth during book club? Hopeless.

One thing the community of readers - traditional and digital - agree on is that with an e-reader, it's impossible to judge a book, or a reader, by its cover.

With e-readers, there's no more walking down an airplane aisle and picking out the passenger who's poring over the same Stieg Larsson novel you are.

"It used to be sort of free advertising for publishers when everyone could see what you were reading," says Jonah Berger, a marketing professor at University of Pennsylvania's Wharton School. "And people would make inferences and start conversations based on what book you were reading."

Perhaps the conversation has merely changed, says Jill Wurman, who reads 50 to 75 books annually. "There's this whole subsection of the book community now that discusses their devices, the editions they read on them, and where the good deals are. I like that it's one more, new way people are talking about books."

Christi Schug, an avid reader and book-club member in Wayne, likes how her Nook, which she nabbed before the item sold out during the 2009 holiday frenzy, allows her to multitask.

"When a friend told me I could read a book and turn the pages with one hand while still holding my wineglass in the other, I knew I had to have one," she jokes. The first book she read on her Nook was David McCullough's biography of Theodore Roosevelt's early years, Mornings on Horseback.

"It was great for reading at the gym. I could make the font real big so that I could read it while on the treadmill, and it was easy to turn pages on the elliptical," she says. However, the device has fallen short for Schug's monthly workout of the mind - her book club.

"I really like to dog-ear a book and mark pages and passages or flip back to remember what a character said when I'm reading for book club, and that is almost impossible to do," she says.

Industry experts agree; the devices can be frustrating for books with family trees, timelines, or anything that detours a reader off the path from beginning to end. "E-readers are for linear books. They are not good for textbooks, magazines or newspapers," explains analyst James McQuivey of Forrester Research. "They are terrible for anything other than what you want to read from page 1 to 300."

Yet plenty of users have found them to be ideal for just that.

"I might be in the mood to start a novel or a chapter in a parenting book," says Melissa Twedt, a Kindle user. "While waiting on the runway for a plane to take off, I decided I wanted to read a different book and ordered it right there."

But electronics aren't always so efficient. Midway through a beach vacation, Twedt's screen died and she was forced to finish reading The Help by Kathryn Stockett on her iPhone. But then the company replaced the device on her return, and with a click, she had all of her books back.

Digital books already account for 5 percent of all book sales and are expected to account for 25 to 50 percent in five years, according to Otis Chandler, founder of Goodreads, a social book cataloging website with more than 3.5 million members.

Some consumers are waiting to see what the debut of Apple's iPad will mean for the e-reader market. Released just over a month ago, 1 million iPads already have been sold. Will the device that had been hailed as "the Jesus tablet" be the category killer of digital readers?

Early signs say no. And yes. Or maybe.

The biggest difference between the iPad and all the other dedicated digital readers is that the iPad is backlit. And for now, that glowing screen is seen as both a bright spot and a lowlight for the iPad.

Schug, like many early adopters of digital readers, expected her device, by virtue of being electronic, to have a lighted screen. So she was sorely disappointed to see it wasn't. "And my husband was even more disappointed - he thought I would be able to read in bed without the light on."

Most digital readers use a specially designed e-ink technology that is easy on the eyes, can be viewed in bright daylight, and can run for more than a week on a single battery charge.

The glossy, backlit iPad screen, while great for a dark bedroom, is terrible for outdoors or near windows, and can run for about 10 hours on a single charge.

One solution:

"I would use my Kindle at the beach or the pool and my iPad in bed or on an airplane," says Doug Alexander, who has been a digital reader since the release of the first-generation Kindle in 2007.

What he doesn't like anymore is reading an actual book. He was forced to read Aleksandr Solzhenitsyn's In the First Circle in softcover because the recently released 800-page translation was not available digitally. "The book was heavy, and I had to carry it around. I hated it, so now I have a list of books I won't read until they show up on the digital platform."

For many readers, book-club members in particular, pagination is a major drawback to digital readers. While a numbered page will be the same in every print copy of the book, not so for e-readers.

Page 275 in a hardcover book might be location 4382 or 67 percent on a Kindle, or page 318 on a Nook. And those page numbers could differ depending on the selected font size.

"There's a bar at the bottom that tells you what percentage of the book you've completed, but I really just want to know what page I'm on," says Wurman, who recently finished reading Wench by Dolen Perkins-Valdez for her book club on her Kindle. Wurman says reading on her Kindle made her realize that she has expectations about plot depending on how far along she is in a book.

"On my Kindle, the endings seem to be more abrupt because I don't have the same physical signs that the end is coming."

That issue aside, Wurman is sold on her Kindle. She likes its fully integrated dictionary that can show her the definition of every word as she reads, and she likes being able to jump from book to book. Her husband's favorite feature? He loves that the page-turning is silent.