I bought it and have read it pretty much cover to cover by now.
The method hasn't changed, but they expand on the information given (obvs a 250 page book is going to have more information in it than a 5 page article). Most valuable to me was the prescriptions for speed/strength/tempo days were much more detailed (in the article, it's basically "do speed work at 5k pace this day", whereas the book tells you exactly what to do).
There's a good bit on strength training, stretching and in-race nutrition/hydration. In fact he is extremely precise with nutrition/hydration.
Also has advice on how to modify the program if you need to (missed days, etc).
Pace charts.
There are some other chapters but those are the big things that you get with the book that you don't get with the article.
Basic takeaway that I had was that there was nothing revolutionary in here (I had read pretty much all the big training books before and had trained with the hansons plan before), but it's nice to have a complete system in one place. And I'm glad I bought it because I've certainly got $12 worth of value out of their plan, so it's nice to throw them a bone.
I do wish it was available on Kindle, though.