This may sound weird, but I actually love staring at my bookshelf. I often will go, pick up a book I haven't thought about in a while, and read it again. I've filled it with (mostly) timeless technical manuals, plate picture books (like pictures of the cosmos, airplanes and things like that), plenty of sci-fi, flight instruction manuals, foreign language dictionaries and other odds and ends. There are plenty of books which I'll buy on Amazon and leave on the shelf for a couple of years and I'll randomly pick one up and start reading.

I think the point here is that a bookshelf makes ideas have a geographic location. With web sites, knowledge doesn't occupy physical space and doesn't have the same permanence which a book occupies. With the bookshelf you're reminded of ideas not because they're hyperlinked together in some ever shifting zeitgeist, but because they're literally sitting right in front of you.