I know on smartphones everything is an app, but these from Agant are mostly auxiliary content plays, interactive titles to accompany other printed work. I was reminded of the glory days of the CD-ROM browsing their portfolio. Content like this has often been beautiful and compelling, but rarely profitable.
The problem on the content front is that you are competing with (1) print / Kindle, (2) the huge library of existing movie and TV content already available for tablets and phones, and (3) the entire internet, where most of the content is free to the reader.
Most of the paid apps that do well add specific functionality to your phone: managing files in the cloud, controlling physical devices, exercise companions, etc. Often they are tied with hosted services: Evernote and Dropbox, for example.
For this reason, I'd imagine Agan saw bigger success with UK Train Times rather than Explore Shakespeare.