The gist of what he is saying for people he'd most likely want to reach but can't for the very same reason he's adressing with his lengthy post:
When reading a long, carefully arranged cohesive body of (text)work, it does not help to be distracted. With ubiquitous access to seemingly useful resources, it is very easy to give into such and deviate from the intended reading material. Book publishers don't seem to get this when devising their solutions for the declining book readership problem.
Another note by me: Good writing is very similar to good programming/programming language design/engineering: a system/text does not get better by adding more to it, but when you can't remove anything from it anymore without changing your intent/its purpose.
Joel gets away with longish posts by illustrating with stories or being funny all he way through. There's nothing wrong with a bit of comic relief if it's relevant or if at least it doesn't distract you. The following joke bought Petzold another screenful's worth of my attention.
Here's some advice for successfully reading a book: You need to stay focused, so try to avoid distractions. Avoid multitasking. Avoid task switching. Turn off the TV. Shift positions occasionally so you don't get cramps or backaches. Don't get too comfortable or you might fall asleep. (Interestingly, many of these same rules apply to having sex, except that you can read a book with a cat in your lap.)
Then again, you need to be sure you can pull it off. There are few things as devastating to your writing as trying to be funny and failing (hi Yegge.)
One of the best books I ever read was "How to Read a Book", written by Mortimer Adler. I think it was written in the 60's or so. I read it in high school and it immediately made me a significantly better reader, and the impact wasn't short lived.
I have to agree with him to some extent. It easy for the mind to wander, and yes, I think thats true for even good books. Having a distraction free environment is a good idea regardless of what you are reading, further, having the ability to write while reading is also important.
Having said that, I have no issues with electronic format of books (except they make my eyes hurt). Sitting at a computer reading a good book works just as well as reading a paper book. If you are that enticed by the web, unplug your ethernet cable.
On a side note, has anyone read "Code: The Hidden Language of Computer Hardware and Software" by the same author. I am halfway through it, and I think its a phenomenal book.
The moment I open a novel by Neil Gaiman and a display ad pops out either asking me to punch the monkey or telling me that I might be interested in something ghostwritten by Tom Clancy is the moment I become a Luddite.
I used to sponsor 3M by keeping a pile of PostIt notes beside me when reading, but paperclips are just as good once you recognise that the smaller inner part of the clip can indicate which side of the page you are marking.
What a silly argument. If the book is good, you will read it anywhere. Who would lock himself up in room just to read a book? Must be bad books. If the book is good, most people will prefer reading it on paper.
Another note by me: Good writing is very similar to good programming/programming language design/engineering: a system/text does not get better by adding more to it, but when you can't remove anything from it anymore without changing your intent/its purpose.
Petzold could have done with a shorter post ;)