Nothing! There are a lot of web-front ends for Calibre, actually. And that’s also why you have some really great iOS apps for accessing your library. For me, the value of Calibre is more in the plugins than the serving mechanism — which is where the bad design becomes frustrating. But again, despite being frustrated by the app, I’m so grateful to the developer for making it, because I would rather have this version of Calibre then no Calibre at all.