It talks about how the made the app, but not how they made the #27 app, which would be more interesting.
The iPad store has so much stuff in it that I don't now how you would get noticed. Once you are in the leader board, it's a different story, but getting there is hard. Did they get a link on some high profile website? Or is it just that "free books" is a pretty good title (even though it really costs $2).
They made the #27 app by having an iPad-tuned app ready on launch day (which by definition will be the day with the fewest competing apps in any category) that probably came back at or near the top of the search results (I think we can safely assume there were a lot of searches for "free books") and whose App Store marketing text and screencaps probably looked slightly better than the other apps in its category (since on launch day there aren't enough ratings to to help distinguish the wheat from the chaff -- appearance is all a buyer has to go by).
There isn't really any lesson to be drawn from this aside from the short-term benefit of being first to market in a category. And even if you find that lesson valuable, it's already too late to apply it.
The iPad store has so much stuff in it that I don't now how you would get noticed. Once you are in the leader board, it's a different story, but getting there is hard. Did they get a link on some high profile website? Or is it just that "free books" is a pretty good title (even though it really costs $2).