You should have written this a few years ago. ;-)
The library doesn't work because of its configuration, it works because the occupants are self selecting. People who want to party go to a bar, instead.
It works because there are lots of areas with different levels of privacy and which tolerate different levels of social interaction, from the carrell in the stacks, to the pairs of lounge chairs by the window, to the reading room, or these days, perhaps a snack bar. Importantly, the occupants of each of these areas are again self selecting.
Finally, library spaces tend to be the commons. Permanent territoriality is discouraged, and this furthers self selection.
There's something about the hushed, low, but unmistakable presence of serious people in a grand room built and utilized for grand purposes. How could you resent working in a space like this?
In college, the libraries where I ended up reading and working were impressively tight, vertical, and often almost claustrophobic [1]. Carrels aren't offices, but the ones I used practically were: there were always walls of books all around each one. The libraries also had big open rooms (similar to the pretty U of Chicago photo superuser2 linked to), and I tried working there a couple times, but even to go into those spaces was supremely uncomfortable for me. It wasn't noise: even if there wasn't a soul in the whole library, I wouldn't go there.
I recently quit my job because they moved to an 'open floor plan'. I just don't think I'm wired to work in flat open spaces. Right now I'm working from home, and though my apartment isn't big, somehow I naturally ended up with walls and (medium-to-tall) furniture surrounding me on 3.5 sides, less than an arm's length in each direction.
[1]: http://3.bp.blogspot.com/-CjyKC0qYp78/TaZz0lPFUyI/AAAAAAAAAN... -- other carrels were even more isolated, but not as photogenic.
Jung : http://en.wikipedia.org/wiki/Collective_unconscious
When we lose ourself in some total focus, we seem to be happy and productive, some explain it with by dropping the individual self We transcend into a zen state ...
I found this very good advice. :)