Reddit reviews Inventing the Way of the Samurai: Nationalism, Internationalism, and Bushido in Modern Japan (The Past and Present Book Series)

For those who want a longer academic piece on the topic, Oleg Benesch's dissertation, Bushidō: The Creation of a Martial Ethic in Late Meiji Japan is freely available as a PDF. Think of it as a rough draft for his book.

Edit: Whoops, I just realized that the tofugu article cites the same link I gave.

Exception

>Taken in the broader context of the Edo period, the Akō Incident is an anomaly, representing possibly the only case of a lord being avenged by his retainers. Of the 118 separate revenge killings recorded during this time, 115 were carried out by family members avenging a slain father, brother, mother, or uncle. Two of the three remaining incidents were perpetrated by non-samurai, leaving the Akō vendetta as a unique case of retainers carrying out a revenge killing during the Edo period.

Inventing the Way of the Samurai: Nationalism, Internationalism, and Bushidō in Modern Japan.

One's lord, at least in theory, was of course very important to a samurai. However, how that theory translates to reality differs from person to person. There were people who committed seppuku to follow their lord in death (it stopped, or at least was minimized, in the Edo because it was outlawed), and there were people who would betray their master for personal(or clan) gains. On the whole I would move to say that, as a group, samurai in the sengoku were a bunch of disloyal thugs.