Also, y'all are a bunch of negative nancys. I'd argue that the biggest point of the book is to give DF a presence outside of the internet and ease new players into the game in a way that the wiki can't. I mean, the wiki is pretty intimidating. I didn't have a problem with it when I started out but not everyone will feel the same way. The articles are lengthy, numerous, and scattered in such a way that it's hard to know where to start. The wiki is unparalleled as a resource but it's a bad introduction. The book is more-or-less meant to be read from front to back, TP has taken care of that for the player. There's something enchanting about a proper, physical manual with lots of illustrations. I remember the first game I couldn't really figure out on my own was morrowind, and the manual really did help. It made the game feel so much more welcoming, there's something sentimental about it that I can't really explain in words.
I don't believe that print copies becoming out-of-date is as much of an issue as you're making it out to be either, things that were not changed in new releases will still be explained by it. Major revamps are usually spaced apart by months of bugfixing and general polishing. I'd say a single copy would be at least 90% accurate for six months. The problem can be further alleviated by simply including the version each copy was based off, a small warning that some information may be out of date and a section with helpful wiki links for "Further Reading."
Call me crazy, but I think the printed copy has more promise than the e-book.