I've never used the iPhone Facebook app, so I can't compare. But fBook's description in the Android Market says it's "a wrapper that optimizes and fixes* the Facebook iPhone web app for your Android phone." The asterisk denotes a list of bug fixes: "1.)...composing message; layout issues 2.) Features: Send SMS, more to come."
It does a lot more than the previously released Statusinator, and it's working well for me so far. It's listed under Applications, Social. Sort by date, as it's fresh today. It seems like a browser pointed to the iPhone version of FB with a different menu, but it doesn't show up in the task switcher so I'm not exactly sure what's going on there. fBook is from Next Mobile Web, who have also offered the excellent Quickpedia, Dial Zero, and PhoneFlix in the Android Market.
Edit: fBook does show in the task switcher. For some reason, not until my second reboot. Also, entering your user ID and pass results in a prompt to have the browser save them. Switching tabs gives you a cool swiping animation, so there is more going on there than a masked browser.
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