I read this long before I ever saw Ghost Dog, and it's really just a collection of statements and comments made by samurai about being samurai. However, there are lots of books and collections, particularly that come out of what I call the Bushido period, where Japanese samurai and Zen philosophers had the time to codify Bushido itself rather than having to go to war all the time. Many of the concepts and peculiarities of samurai came out of this period of reflection. During the Sengoku period (Age of the Country at War, or the Feudal Japanese Civil War), the notion of a samurai more than just being a guy who happens to be paid to fight on behalf of his employer was somewhat laughable. Any man back then who found a sword could call himself a samurai. Prior to that period, samurai ethics and honor was formulating in order to differentiate a samurai, which is really a knight if you think about it, from the common soldier was percolating, but it wasn't until the Tokugawa period and beyond that Bushido comes into some sort of cohesion.
Compared this with the code of Chivalry in Europe. There are similarities, but if you really get into Chivalry, it's really a much more honorable approach to war than Bushido. The difference, I would say (having doing a dissertation and a thesis in college of the two codes) is that Bushido focuses one's duty to one's master, in this case the guy who's paying you (not just in money, but by giving you a house, some land, some servants, maybe even a wife), versus in Chivalry, where your first duty is always to Christ. Every knight who becomes one always first swears to defend the faith. And this is critical to understand the difference.
Bushido tends to draw the line at what is dishonorable in and of itself by virtue of whatever your duty is to your lord. Meaning, if your lord orders you to do something despicable, even cowardly, something that runs against what is considered honorable, it is still honorable to obey. If you choose to disobey, the honorable thing to do, to protect your own family's honor (and maybe their lives) is to commit seppuku, which is ritual suicide. This is because, in general, Eastern philosophy tends to see the world through the lens of Order v. Chaos, and that Order in and of itself is Good and therefore no evil can come out of Order, while Chaos is inherently Evil and no good can come out of that. Which is why you would see countless atrocities committed in China, Korea, and Japan throughout their histories that would make Europeans blush with shame had such atrocities occurred over there. Not to say that they didn't happen, but to the Eastern mindset, Order was achieved, and therefore they do not commiserate about it the way the European Christian would.
Contrast that with Western Philosophy epitomized by Catholicism. Unlike the Eastern view, Western Philosophy (from Socrates to St. Thomas More) sees the world through the lens of Good v. Evil, and that Order can come from Good, but sometimes so can some Chaos, and vice versa. That Order, in and of itself is not the goal, but Goodness is the goal, and Order, if it comes, is merely a by-product.
This is important because it dove-tails into the Catholic view of Just War, which is essential to understanding Chivalry. A Knight must be courageous, virtuous, and True. He must defend the weak from the strong, and always be ready to render mercy to the fallen and the defeated. Surrender of a foe, while not entirely an honorable thing, is not regarded entirely as disgraceful as a samurai would see it. Those that willingly surrender are given mercy and dignity (under the ideals of Chivalry) because it is preventing a needless loss of life, which is important. Even if he is not employed (a Knight-Errant), the Knight must respect the edicts of the Christian king or lord of the land, unless they contradict God's Law (God outranks everyone). If war must be waged, the reasons for that war must be justified under Christian doctrine (if you watch the Shakespeare play Henry V, the first scene consists of a pair of bishops consulting the young king and his court on why they have a right to go to war over the Saliqueland, because this is really a test by the French monarch to see if the new young king has the stones to fight for what's his, and one could say that such a test is in violation of God's Justice). This is important because if the king doesn't have the moral justification for war, he would have a lot of trouble getting knights to fight for his cause, even if he's paying them.
Of course, both Bushido and Chivalry are ideals, and humans have a hard time living up to ideals. Mistakes are often made, and the human heart is fickle.
No. And you need to get more educated if that is what you took away from that text. He pointed out why mass mobilizing murder is not reflected over in Asia, because they have a very different mind set. Compare the soul searching in Germany and Hungary over the holocaust, or even in western UN countries over the srebreniza massacre, to the Japanese refusal to reflect over their war crimes, or even the chinese hangup on Japanese atrocities, while ignoring the murders of millions of chinese by China the last two generations.