I don't think a Article and a Book can be properly compared. I also suspect that Harry Potter won't be out of print (digitally or otherwise), and as of now has a clear copyright holder to which you could ask (likes like original Times article includes interview with original author and may have their consent for what thats worth).

Each case is on its merits, and this is far from clear-cut. It is my opinion that this is very well fair use but there are plenty of opposing view-points here.