I went over to the Pocket website today, they are using Chaparral Pro on the web reader (see attached file). Definitely inferior to FF Yoga on the Android version. I'm kind of surprised they would change their look so much between web and mobile, but I guess the ease with which one can extract fonts embedded in websites is a concern.
Though for that matter, apk files (android apps) are really just zip files with an alternative extension. If one really wanted to get their hands on a font seen in an apk, one might download it, unzip it, and look in the 'assets' folder. Of course, this would violate the licensing agreement of the font and therefore be illegal in most places, so of course I'm not recommending such an action.
For what it's worth, I find that Arno Pro does a pretty good job on my Aura 6", very comfortable newspaper-esque font. A quick duckduckgo search turns up some free downloads, for instance
here.
Cheers!