A good book that is a little general but one that I found useful is The Samurai sourcebook by Stephen Turnbull. As with all sourcebooks it has a lot of information with a pretty decent section on the clans and the leaders of the era.
I'm curious to know the arguments from these historians about how Japan wasn't a feudal society. Most retainers held lands as fiefs by the will of their superiors, in exchange of service, income, and maintaining troops, and were held by oath, duty, or honor to serve his Lord to the death.
Here in the West, it is the core definition of feodality, from which the whole feudalism system originates. Its centered around the gesture of the hommage, which binds the overlord to his vassal, by the solemn promise to serve and being tied in service to a lord. The only difference I see in Japan, is that retainers didn't have to make a solemn oath about it, as service was the core definition of being a samurai in the first place.