Perhaps it is better to word any sentence about "Progress  
and Poverty" to the effect that, _in its day_, it was a best-seller. Half  
a century later not only was the population bigger, the reading population  
was bigger, and as time went on the market for books read by college  
students had its effect. So comparisons of books written many years ago  
would need to be adjusted for that.  
 
I do have some numbers for comparison. The Beveridge Report (1942)  
reportedly sold around 500,000 copies in England within a very short time.  
Hayek's The Road to Serfdom over its long history sold around 250,000, if  
we count only the ones sold by U Chicago Press. Routledge's edition would  
add some number more, and there were 16 translations, so that would add  
more - as far as I can tell, no one knows the ultimate number. But if we  
count in also the Reader's Digest 20 page condensation done by Max  
Eastman, the number explodes. RD had a circulation of about 10 million in  
1945 when the condensation appeared, and over a million reprints of the  
article were also distributed. Most people who have heard of The Road to  
Serfdom do so  by knowing of or reading the condensation.  
 
I would think that some of Galbraith's books would certainly be way up  
there if you look for 20th century bestsellers.  
 
I don't think textbooks should count  - required books shouldn't count. I  
wonder if books like _The Organization Man_ or that guide to finance  
written by "Adam Smith" (a pseudonym) should count?  Good luck.... 
 
Bruce Caldwell