Entourage shut down their website on Sunday and have replaced the Edge Store with a closing notice. The device registration servers will stay up, but right now the only thing you can do on the Entourage website is read this notice. You'll need to download any ebooks you bought from Entourage by 27 May; that's when the ebook servers will be shut down.
This shouldn't come as a surprise. there have been a bunch of complaints the past few weeks that the forums hosted on the Entourage website have been having problems. New Registration seem to have been not working and there was no response from messages sent to then moderators.
I hope this doesn't mean the company will close. That would be a shame. This was a fun device.