This was my first time ordering from Amazon JP too, so believe me, I understand. Check out this thread, specifically the questions I asked and the answers I got (the link starts at one of my questions). Hopefully that will help put your mind at ease. Once I actually ordered, everything went very smoothly.
I’m going to close the poll for the next book shortly. Sometime today I will create a “home thread” that will include some polls for the reading schedule. One of them will be when to start reading. As @windupbird said, it will be 2-4 weeks from the end of Kiki to make sure everyone has enough time to get the book and give those of us reading Kiki a short break.
Again, as @windupbird said, we will only do the first volume of Aria the Masterpiece (Aqua volumes 1 and 2) to start. The second volume can be on the next poll if we want. I want to note however, that Aqua is only two volumes, so Aria the Masterpiece volume 1 is the entirety of Aqua.
Also, Aria is fundamentally different from Yotsuba because it has a long term story. For that reason, I really don’t think we should go beyond volume 2 of Aria the Masterpiece (Aria volumes 1 and 2) as part of this book club, and maybe not even that (and obviously only if it wins again anyway). If there is enough interest, we can create a separate book club like they did for Yotsuba so that we can continue reading it. It’s important to make sure this book club is always open to new members, and reading long series goes against that.