I'm an american, and I am familiar and comfortable with standard roundabouts. I prefer them to stoplights/4-way stops in many cases. But for the life of me, I cannot understand what road configuration would demand a double roundabout. You could have ten roads meet in a single... so why use two roundabouts for four roads meeting?

I'm also curious as to how they should be navigated. If I ever find myself driving in your country, I'd love to not be nervous about this. I've heard that you're supposed to treat them as separate roundabouts-- does that mean you can't transfer from one to the other?