How do you like your reference material?

By looking at my desk on any given day, one would have to conclude that I prefer my reference material in the form of books.  I no longer even attempt to put some of them back in the bookcase.  Some of them lay open to the last topic I was researching or just generally reading about.  One on top of the other, both to the right and left of my work space.  Yes I like books.  I also use various web sites for shorter reads, discussion insights, new stuff (until it’s published in books) and the like.  I have a few books in pdf format that I use on my screen.   As easy and simple as that is, I just don’t use them all that much.  Time and time again I reach for the physical book and not the electronic one.  How about you?  Let me know your preference.