But don't go jumping to any conclusions: this doujinshi, titled Throw Line, isn't porn, and it's not really a “manga”-type doujinshi either, in the sense of being a sequential story. It's a collection of illustrations and sketches, with 12 color pages and 13 black and white pictures. So it's basically a self-published elecronic artbook. But it's Range Murata, so it's cool.
The app is available in Japan and the U.S., apparently, which leaves everyone else out, unfortunately. But hey, it's a start towards seeing more of this sort of thing abroad, at least...although it'd be cooler if you COULD get pornographic doujinshi. Silly closed-minded Apple.
Anyway, those of you who wanna see buy it, here's the iTunes link.