If you will be traveling anyway, its a way to pick up a little cash. I wouldn't make a special trip to do it. Right now I've got a book to go back to London and a package for somebody in Shanghai. I'll deliver them when I get around to it.
Maybe Ben will need to add a Catagory like
The Librarian said Dogberta is still carrying one of the Library's books around. You can get the reward if you track her down and remind her to return it - lol