dynamics of the textbook industry - a quick thought

Some sentences to ponder regarding the dynamics of the textbook industry, from New Perspectives on Keynes by Cottrell and Lawlor:

Principal features of Samuelson's text remain unchanged over a period of forty-six years. We have argued that Samuelson's 'son' of Keynes was really the product of a virgin birth; it also appears true that, in common with other products of immaculate conception, the analytical apparatus of Samuelson's Economics has remained unsullied by its confrontation with the world. the larger uses of that apparatus have also remained unchanged: Samuelson of the eleventh edition remains the harmonist and neutral scientist of the first edition.

The authors are being less praising of Samuelson than they might seem, given this quote. As they observe in a footnote, Samuelson lost significant market power as early as the mid 60s. His text might have been praised as an excellent model of how to educate undergraduates, but that's not all what sells in the textbook industry. Politics and approach play a significant role -- which is a big reason (though not the whole reason) why big-name centrists (Mankiw), or smaller-name economists who keep a close ear to the ground for ideological shifts in the mainstream (what McConnell was), end up being the most successful.