Lots of people pointed to the way the world's music buying habits shifted from buying CDs to buying MP3s (before it shifted again, to streaming) as an argument for why e-books would inevitably displace printed ones. But there was a fundamental difference between those two examples, namely that the music industry abandoned tying digital purchases to a single device via DRM relatively quickly, while the e-book industry held doggedly to the idea that e-books bought from Amazon should only work on Kindles, e-books from B&N should only work on Nooks, etc. Which made e-books notably less appealing from the buyer's standpoint; with digital music you could have a reasonable assurance that your purchase today would play on the device you own tomorrow. With e-books, you could not, and you still can't.
(Yes yes, I know about Calibre and so forth. I'm talking here about how these things looked from the perspective of the average person.)
It's a great example of how all the players in a competitive market can hurt their long-term interests by relentlessly pursuing their short-term ones. It was in everyone's short-term interest to try and grab more market share at the expense of their competitors by locking customers into a closed ecosystem. But by doing so they passed up the opportunity to grow the entire market. And a small slice of a huge pie beats a big slice of a small one any day.