Interesting. I have the reverse effect - it's much easier to concentrate on the physical books, which don't need to constantly compete for attention with all the distractions of the web, like the impulse to check your e-mail every five minutes.
That's mostly just for long books, though - reading comment threads such as on LW isn't a problem. The hypothesis below, that it's because of their discretized nature, sounds quite plausible.
Dale McGowan writes:
In this spirit, I propose the creation of a fully off-topic discussion thread.
Here is our monthly place to discuss topics entirely unrelated to Less Wrong that (of course) have not appeared in recent posts.
ETA: There are two behaviors I would love to see associated with this thread. First of all, discussions often drift off-topic in the middle of a thread. In these cases "let's take this to the off-topic thread" would be an excellent response. Secondly, given who's doing the discussing, I could easily see, say, a discussion about recent developments in some webcomic blossoming into a LW-worthy insight, in which case someone could spawn a new thread.