Update: I went to KinoK this evening pick up my specially ordered edition of YAnimal (they called me last week for the prior issue I ordered), and I thought it'd be a good chance to look for my missing volumes. I picked up volume 22! And, I saw an art book by the author called 'Water' which I also picked up. It's BEAUTIFUL inside, wow.
There's another Vagabond artbook called
Sumi that showcases Inoue's spectacular ink work throughout the series. It's not as colorful, but it's no less beautiful.
I also picked up the Claymore book which came newly to the store, and I'd been eying the VHD art book for a while, so I figured why not, get broke worse while you're at it aha ha ha ha >_>'
That VHD Amano artbook looks particularly intriguing.
I put in a special order for the other missing volumes, and it looks like 4, 7, 15, 16 are out of print and while they've put in my request, they're not sure they'd get it haha! Wow. Sucks for me.
Yeah, that's the major hazard of going back and trying to get the original volumes as opposed to the VizBigs. Hopefully it's just a gap between the original printing and the second editions of those volumes. Which makes some sense for volumes 15 and 16 since the image you posted of your volumes shows that the reprints go to at least volume 14, but that doesn't explain the unavailability of 4 and 7, unless the second printing sold out as well or they simply didn't reprint those volumes? Strange, in any case, I'll see what I can do for you.