It's no mystery that e-books are super popular. Readers love e-books because they're incredibly portable and usually cheaper. Publishers love them because the margins are better, and they yield all sorts of useful data about sales patterns. Authors love them because e-books empower them to cut out publishers. Now that the technology is swimming in the mainstream, it's clear that the books world will never be the same. However, with such a seismic shift in the industry, there have been some unintended economic consequences for other worlds, too.

As readers are building out their digital libraries, it should come as no surprise that their physical libraries are changing, and the furniture industry is responding accordingly. The Economist reports:

Next month IKEA will introduce a new, deeper version of its ubiquitous “BILLY” bookcase. The flat-pack furniture giant is already promoting glass doors for its bookshelves. The firm reckons customers will increasingly use them for ornaments, tchotchkes and the odd coffee-table tome--anything, that is, except books that are actually read.

Diehard ink-and-tree fanatics must gasp at the notion that bookshelves are no longer being built for books. But this doesn't mean that people are reading less. In fact, some people say that e-books are getting people to read more. Meanwhile, a cottage industry is emerging for decorative books. Earlier this year, The New York Times covered the burgeoning business of selling hardback books by the foot, for the sole purpose of giving (rich) people's homes that scholarly look. "I could have hung art," one buyer told the paper. "But I like the textural feeling of shelves, and of books on display."

E-books are changing the economics of education, too. With the ballooning price of textbooks, nonprofits are pushing for wider adoption of e-books in schools and colleges. A new campaign called "Textbook Rebellion" that promotes the adoption of cheaper and free e-books instead of the bulky, very pricey textbooks that can strain students' bank accounts. College bookstores are catching on, too. "Nowadays most college bookstores offer a digital textbook as an option right on the bookshelf next to the hardback," The Boston Globe reports. "Students pick up a card, which resembles a gift card, and redeem it at the register." However, the education world still has a ways to go with only 25 percent of new textbooks currently available in digital form.

If you're still not sold on the "seismic shift" idea, you should be. Amazon's e-book sales zoomed past their hardback sales over a year ago, thanks to the runaway success of the Kindle. Brick-and-mortar bookshop behemoths are following Amazon, starting to resemble electronics stores--changes to the features of Barnes and Noble's Nook are covered by tech bloggers just like any other any other gadget--and those that aren't keeping pace (Borders) are going under. Publishers are completely revamping their business models. And some authors are even skipping the hardback round altogether and self-publishing their work as e-books. It's also created entirely new sources of revenue for newspapers and blogs. Ars Technica recently made $15,000 selling a free article as an e-book.

There's still progress to be made. Publishers are just starting to experiment with the possibilities of e-books and the app ecosystem that they enable. Though complex rules from gatekeepers like Apple and Amazon can slow innovation, the publishing world and those industries supported by publishing--like the bookshelf industry--are now beholden to that old adage: Innovate or die. And who could say no to innovation?