As a 26-year-old techie, I can say that I haven't gotten a digital reader and don't plan on it. While I hope this means that textbooks will be downloadable, making all classwork convenient, allowing students to carry all course materials at once, and most importantly, dropping the excessive cost of textbooks, I also believe nothing will replace books, nor is publishing in danger.
First of all, even digitized books need to be published. An online magazine is published. Pay-to-download sheet music is published. Just because it's not in paper form doesn't mean we won't need publishers and be paying for rights (and writers getting royalties), it's just not the typical concept of publishing.
Secondly, many elderly people have no interest in using such devices. Though my grandma was very smart and always paying attention to the latest trends, she never got a computer and didn't want any electronic devices except her DVD/VHS player and CD player. The retirement crowd is huge right now and they have spent their whole lives with physical books. Between the learning curve, the initial cost, and the problems they may have with reading the sometimes dull, glare-happy, or blurry screens/text, a huge group will be taken out of the picture.
As for children, they learn through sight AND touch, so your wife should know the huge disadvantage of e-readers for the early reading crowd. No parent will want to give a child (or maybe even teen) a costly and delicate device like an e-reader. In addition, with no tactile response, such as books with buttons that make sounds, have patches that feel fuzzy, scratchy, like grass, furry, etc, there is no interaction, therefore a huge deficiency in an e-reader's ability to teach kids to read. It's much more effective to read "bunny", then see one in color, and feel soft fur on the page.
This leads to another issue--color. Generally, e-readers use 'digital ink' and are colorless, making them sterile and boring. Libraries and bookstores work because vivid colors and text pop out and scream "read me", "buy me". When everything is literally a shade of gray, the distinctiveness of the famous black/red/white Twilight book covers, the paintings in The Polar Express, and the simple visual appeal of a shelf full of books in your house will be non-existent. Does anyone want to read an art history book in which all paintings have been removed of their color, like a Xeroxed shadow? Will you want to travel to Italy looking at a digital travel magazine missing the colors of wine country, Tuscany, modern Rome, and the first opera houses?
Lastly, books are social. You can loan a book to a friend. Will you loan your e-reader and all 4,000 books? If it's transferred to them digitally, will books suffer the same fate as music? Will lawmakers fight literary piracy as fiercely as music piracy?
A book is meant to be held, smelled, enjoyed, passed around, written in, highlighted, readable by a group looking at the same pages, and showing signs someone's read it, someone cared enough to pick it up. A stain is a badge of honor. I'd rather drop tomato sauce on my cookbook than an e-reader.

I think a useful analog is what happened when music transitioned to the CD. For the majority of users, this meant no more music on vinyl, but the thing is records never truly went away. According to Reuters, there were nearly 2 million vinyl records sold in 2008, with an estimate of 3 million records to be sold in 2009. This is new record sales, not even factoring in smaller record stores or the used market. Among audiophiles and collectors, there remains a small but dedicated group of people who are fiercely loyal to albums. They typically site experiential qualities such as the "warmth" of the sound that records produce, or even the full-sized cover art when they explain their dedication (both of which explain why cassettes have not enjoyed a similar loyalty). Jack White of the White Stripes explained his own dedication to vinyl on NPR:
"Vinyl is (the) real deal. I’ve always felt that until you buy the vinyl record, you just don’t own the album … It’s not just me, it’s not just a little pet thing, it’s not just some retro romantic thing from the past. It’s still alive."

There is a similar loyalty to the experience of books that I hear from many of the devoted bibliophiles that I know. The feel of the paper as they rifle through pages, sometimes looking ahead, or flipping back to an earlier passage to enjoy its full meaning based on the book's most recent revelation... these are the sorts of experiential qualities that most bibliophiles that I know have no interest in giving up completely.

There is one final lesson from vinyl that I believe will apply to books as well. Thirty years after Phillips introduced the first consumer CD player, there are still many records that have never been republished on a digital media. If you want to get these out of print recordings, the only way that you can do so is to find them on vinyl. I suspect that there will be a similar catalog of highly collectible books that won't make economic sense to republish, but will still be sought after by collectors and bibliophiles.

I believe that books will always have a dedicated, if niche, following similar to the following that vinyl records have. I am a utilitarian, but I am also a bibliophile. I don't think it will ultimately make sense to publish all works as physical books, but I think there will always be physical books that make sense, and I do believe they are worth fighting for, though I don't think a fight will be necessary to protect a niche book trade. I suspect that the book stores of the distant future will be similar in nature to vinyl record stores of today...small, specialized, higher margin businesses with staff that run the place more for love than for money. My encouragement to your wife would be this...opportunities seem to have a way of arising for people with a genuine love of what they do, often because they are dedicated enough to their vision to create the opportunities themselves.

First off, I work in a public library and I don't see the end of books yet. There are several libraries making headlines for getting rid of all their books and going with the Kindle/Nook/whatever but they will only offer a hand-full of those for students to use, otherwise the student has to have their own. What will those students who can't afford one do? They will be hurt academically if none of the readers are available for them to use. I know everyone thinks that you can find everything on the internet but can you trust everything 100%?? Not even 25%! I think books are here to stay! Who wants to use electronics while relaxing in the tub or at the beach or anywhere little hands can get slimy fingerprints all over the screen...
Your wife is a MLS student - tell her to check out FW Lancaster's Toward a paperless society - nearly 30 years after he wrote this, he has totally changed his stance on it. Here's an article about his paperless society and his more recent feelings and what others have to say about it all - http://www.thefreelibrary.com/Aftermath+of+a+prediction%3a+F.+W.+Lancaster+and+the+paperless+society.-a0184699136

I see your point Corey as I have been steadily filling my iPad with books and no matter how many eBooks? I buy the little pad will not get any heavier.. moving will be a breeze in the future. Children of today will be the college students and young professionals of tomorrow and might not ever know the pleasure of carrying incredibly heavy cardboard boxes of books up and down stairs, back and forth to the car or even the pleasure of lugging a duffel bag or back pack full of textbooks to and from school.

Libraries on the other hand I believe have a lot of life left in them as they do sooo sooo sooo much more than store books, periodicals, and card catalogs.. the Dewey decimal system will never die.

Check this out ~>These are the community and educational activities for adults and children offered at my public library <~ that will never be replaced by a tablet, Kindle, iPad, Nook, or eBook reader of any kind. My library offers so many things for so many people in my community that people line up at 8:45am for the door to open at 9:00am.

@mikebracco asked a related question and my answer (linked below) to it described in greater detail the commendable and virtually irreplaceable community outreach, educational, and entertainment activities the public library in my neighborhood offers. Tell you wife I believe her job as a librarian might be evolving but the need for that position has a lot of energy, life, and necessity left in it... especially for children.

With the internet at our fingertips, do we need libraries anymore?

Libraries might become smaller and their roles will evolve but they will not go away but I feel their role in education and community is to great for them to disappear. Regular printed books and traditional bookstores I feel are not going to be so lucky, their time is over and their life is short. The convenience of eBooks and tablet computers will really begin to outweigh the usefulness of regular printed books to most people save the true printed book collector or nostalgic home decorator.

One thing that makes me confident (or at least makes me hope) that books never go away is tutorials for computer programming, such as those put out by O'Reilly.

I have never, every felt comfortable with trying to learn a computer language on a pdf, on an e-reader, or any other electronic means. I need to have that physical book propped up next to my keyboard, otherwise it just doesn't seem to work for me.

There will always be Children's Literature, AKA Kiddie Lit. This is a fiercely competitive field, and it's primarily based around "analog books." No one - not even James Cameron - can invent a real pop-up book for an electronic device! Little kids start with cardboard books, then are encouraged to read in pre-school. Children who are read to by parents are said to be more well-balanced, and I don't envision a lot of parents, at least for a long time, having the bed-time story be on a Kindle. "Hop on Pop" and other Seuss titles - are they available for Kindle, etc.? I wouldn't think anyone would bother, really. So if kids are raised with ink and paper, it'll be around for a long time. Now magazines and newspapers may be a different story...

Note: I paused to look at available Kindle titles. Dr. Seuss is not available on Kindle. There you have it!