I don't think pictures are necessary. I think that one thing turning people off of books is that they cost a lot for what you actually get. $14 to try a book that you might not like isn't a good thng. $2.50-$5.00 is more likely to be something you'd buy on impulse, and cheap enough that you don't have to worry about junior spending his allowance on a book.
If the book costs $15 plus tax, you could get a CD for the same. Heck you can get an old ps2 game for $6-7. Which would the average teen-20something rather have 4 xbox games or 1 book? I'm not sure how many people would really spend almost $20 on something that they can't try first.
There's the time crunch issue as well -- we have less time today than we did 20 years ago. A 300 page book can take upwards of a week to read through, and if you have to put the thing down for a week, you forget what was happening.
I'm a bit suspicious that it's quality holding down the book industry too. Most of them aren't all that great. Crimies are CSI: The Book, SciFis all want to either be Halo, Wars, Trek, or actually are fan fiction, Romances are dull, there just isn't much out there that makes me think "Ive never seen this before".