First, I want to say thank you to those who patiently listened as I whined and complained about this VN as I played it. I should also explain what I was complaining about first, so that people don't get the impression that this is an awful VN, just because I have complaints about it. I'll place this in spoilers for people who don't care about my whining.
Basically, I have a pet peeve when it comes to people who use 'alternate history' settings. It isn't the fact that it is an alternate history... it is when they fail to account for impossibilities that are outside of the central historical difference. In this case, I refer to the situation of the Chinese in this game... to be blunt, China didn't have the ability to project power across the Sea of Japan in the era just after WWII (they were still busy with their civil war, then the disasters of Mao's early rule). The US was able to because they had the ships, planes, and trained troops necessary to maintain a presence in foreign land, not to mention the wealth necessary to keep them supplied overseas. This particular hole in the setting drove me nearly insane from the very beginning, but I realize it isn't that important to people who just want to read a good story, so I'll leave it at that.
Second, I should say that I have a firm belief that Ryukishi's VNs make better anime than they do VNs, because his scenario design is far better than his writing (not to mention his art). His love for torturing and killing his own characters is very similar to that of George Martin or Glen Cook, but he mixes it up with that peculiar disconnect from reality and surrealism that is unique to Japanese writers, especially when it comes to violence or sex, lol.
The first part of this story looks like it comes out from a Japanese-colored version of our own film noir. To be honest, I found it pretty amusing and an overall fun ride. I cried and laughed with the characters, and I got to like the various people Rose and her crew met. The second part is somewhat less amusing, as it is mixed in with hope followed by a quick fall into despair, as things take a turn for the worse that never quite gets better. The third and last arc (there are four seasons but only three arcs, really) is devastatingly emotional and full of a despair far surpassing that of the first two. Friends die, others betray, and characters you have come to love suffer. In other words, it has all the ingredients you need for a good trilogy (which is what it feels like).
The themes involved will probably confuse about fifty percent of those who read this who aren't from Asia. I'm not kidding. Simply put, it requires the ability to appreciate the character, weaknesses and strengths of the Chinese, Americans, and Japanese at the same time. As such, the learning curve for fully appreciating this VN is a bit steep. In fact, in some ways it is more steep than I/O because the matters it deals with aren't matters of science but of culture and people.
I suggest anyone who wants to fully understand a lot of what they say - especially the exchanges between the Chinese mafia and Rose's people - read up on current events in the relations between Japan and China, because this story has been heavily influenced by the recent mess in diplomatic relations between the two. A lot of it is mixed up with the usual emotionalism that defines Japanese writing, but the core arguments are based in current events, rather than just ones of the distant past.
Is this a good VN? That's an excellent question, me. To be honest, it is hard to say. There are a ridiculous number of flaws to the setting, and the writing, while much better than Ryuukishi07's past efforts, is still less than poetic (and his event descriptions are still as weak as ever). However, if you just look at the fun factor...? This is a fairly enjoyable experience. Oh, for those who hate to see characters they like suffer or die off or who can't deal with concepts like prostitution, organized crime, or corruption as a matter of daily life this would be a hard VN to read. In some ways, this is far darker than his past VNs, because the actual daily events include no sense of fantasy, save for the setting itself. As a result, people who could enjoy Higurashi, Umineko, and Higanbana with no problems might very well show signs of rejection with this one. At the same time, people who despised the others might very well like this one, because - while it does share all of Ryuukishi's usual habits - both bad and good - it is outside of his usual ballpark in the subject matter.
Edit2: Whoops, the last edit was a bit too... sharp. To avoid controversy I have sealed it behind a spoiler tag. Read at your own risk.
Edit: I should have mentioned this before, but Ryukishi pretty much abandons all combat description in this VN in favor of using the button-press minigames and comic-like pictures to cover for his lack of talent in this area (he really doesn't possess any in this area, in my experience).