This Mistborn one, which I also happen to be reading at the moment. Just finished the first book a few hours ago and I literally can't deal.
But as for the set itself, I really like the art in general and it also comes with a lovely map/poster. I know it's probably not that great, but I barely own any box sets.
I have these editions of Mistborn and I think they would be what you consider "floppy". They are paperback and they stay open very nicely.