Bookish has been in development for over 2 years now, so it was something of a surprise that their apps don't offer the same functions as the website. The new app looks to be a standard Epub ebook app from Bluefire, a specialist in this niche, and will let you read Epub and PDF that you buy from Bookish.
When Bookish launched several weeks ago it was touted as being a new online community that would help members discover their next read. It has been likened to a cross between GoodReads and Amazon, only without that pesky independence (Bookish is owned by Penguin, Hachette, and S&S) and without Amazon's recommendation engine.
You can find the new app in iTunes. Bookish also has an Android app in.
I have been trying the website myself, and about the only interesting detail I have uncovered is the rather bizarre TOS (the ones which promise to ban you from the site for referring to the TOS as bizarre). After 2 weeks I still don't see what this site offers that makes it better than the competition. Anyone?