First I will say that Settlers isn't primarily a theory book, but rather a history book with a guiding central thesis. In reading it, you'll find that it often doesn't define the undercurrents or do analysis of, the historical events it focuses on. Its less "analysis" and more "history" focused, but of course it does have a few central ideas and themes that Sakai feels drives US history.

The main thesis of settlers stands, that is proven thoroughly throughout, is that the US perfected a system of socialized bribery that allowed a minority of capitalists and slave-owners to recruit white settlers from europe, to form a settler garrison in the US, and gain from the genocide and conquering of hundreds of Indian tribes, and to steal the country from coast to coast, in a phase of orgiastic primitive accumulation. The bourgeoisie then continually invented new ways for this absorption into the murican dream and whiteness to occur, and had a mass base to carry out their goals, always at the expense of the oppressed nations living within the US's borders, the black nation, the indian nation, etc whose class interests were at odds with the settlers, and who had no path out of exploitation.

TL:DR; want some free land? All you gotta do is kill some indians to get it. And thousands of poor white proles from europe very loudly said yes.

Its an expose of the US's settler-colonialist foundations, its history of genocide, exploitation, social bribery, and the spoils that went to those who willingly absorbed into whiteness and the murican dream (even if they had to kill indians to get some cheap land to do so.) Also has an excellent and unique analysis of FDR's new deal as the bribery and absorption of the labor movement into settler colonialism that I haven't seen elsewhere.

The spats with other leftists, and detractions from the book are really incidental IMO... the "READ SETTLERS" meme is important because there's nothing more dangerous to the pride of western leftists than telling them they're likely descended from generations of bastards. Making sure people don't read settlers is the best way they can defend their identity and race pride, which must be eradicated for any true internationalism to arise. This book really separates the social chauvinists from the internationalists.

Also there's a tendency for imperialist leftists to dismiss the book by calling Sakai racist, or claim that he was a race essentialist, which has been disproven many times: Settlers probably more than any other book first elucidated the complicated overlap between race and class; how they are inextricable, and how those US leftists who attempt to split the two are committing a mistake, and have their progenitors in the history of the US labor movement.

Oh one other thing, the New Afrikan thing doesn't have to do with Maoism (In a post-interview that I recorded as part of the audiobook, he talks about how he has great respect for mao, but he isn't MZT or MLM), it has to do with the idea of "colonized nations within the borders of empire": IE peoples with shared traditions, origins, and class interests, that should make up a nation with its own autonomy and system of governance, but is prevented from doing so. This is "the right of nations to self-determination", but within the US's borders, that everyone from Malcolm X to Indigenous leaders to puerto rican anti-imperialists pushed for.