Encyclopedia Britannica announced that it was cancelling future publication of it's print edition due to falling sales. I'm not sure too many people were surprised considering the internet has become a free, on-demand resource for most people. The Encyclopedia Britannica was 32 volumes, $1,395, and outdated before you got it in your house.
Wikipedia is one of the reasons print, and even online subscription based, encyclopedias are failing. There are also millions of web sites that have information and resources that are interactive and free.
I remember my parents getting us an encyclopedia and being so happy I didn't have to bike to the library as much any more. Now, I can get more information than that in my smartphone. Online resources are constantly updated, link to other resources, and can be interactive with video, audio, and activities. It seems like textbooks are, or should be, going the way of the Dodo along with the encyclopedia.
The infographic below is a comparison of some data about Wikipedia and Encyclopedia Britannica.
What I use with Physics classes instead of textbook