It can, but if you're building web apps instead of web sites with a little custom functionality it will make your life needlessly difficult.http://ask.slashdot.org/story/11/12/04/2227209/ask-slashdot-one-framework-to-rule-them-all#

It's more subtle than that. The Dutch schoolmaster CIO only has two pieces of software to choose from, one of which is a bunch of outdated Windows desktop apps that are terrible to work with and the one TFA is about, which is a fairly decent set of web apps that unfortunately have never worked on anything but windows (first they used all sorts of ActiveX components, now it's a bunch of Silverlight crap, apparently). So there really is very little the schoolmaster CIO can do, and given the lack of options, he probably made the best possible choice.

Technically speaking, Drupal 6 does not have elements like "Left Column" and "Right Column". If you base your themes on the Zen base theme, you can have whatever "column" you want. I'm assuming (I'm not a themer with in depth knowledge on the subject) this is because Drupal 6, too, has a notion of regions. There's probably a lot you can learn from this book that will still be applicable to Drupal 7 (the differences aren't huge). That said, I don't see why they didn't just do a quick rewrite to incorporate the main changes and slap a Drupal 7 title on the book, the way they did with the Pro Drupal Development book.