Why should textbooks not count? Is Bruce making the claim that if one is  
required to read a book, the significance of one's reading is somehow less  
than if one is not? If so, why? Could one equally validly argue that people  
who subscribed to Reader's Digest did not even choose to buy the condensation  
of Hayek's RTS and may not even have looked at those pages. This raises the  
interesting question of why one is interested in what were the best sellers. 
 
There is also the problem of what counts as a textbook. I do not see the case  
for considering _Progres and Poverty_ but ruling out of consideration, say,  
Mill's _Principles_ or Marshall's _Principles_ on the grounds that they were  
used as textbooks as well as being read by the general public.  
 
Roger Backhouse