I haven't played any of the Atelier games but the artstyle really fascinates me. Apparently the director for this is also the director of Blue Reflection? Which I thoroughly enjoyed and hopefully she's making a third game.
I'm in the process of hunting down copies of the Mysterious (got Sophie, Firis and Sophie 2) and Secret (got the first one) trilogies. I also have Yumia.
Planning on playing Mysterious first because it's the oldest.