This book was a classic of its time. It showed that Canada was a class society. The universities, business, political parties, the legal profession,government bureaucracies, the accounting profession, the cultural organizations and most other elites in Canada were dominated by Anglo-Saxon protestants. Thus the book gave license to socialists to claim that Canada was a country with an unjust class system while non-Wasps could claim that they were frozen out of positions of power.
While there was certainly some truth to what John Porter had to say he may have overstated the his case. Conservatives would have said that he was exaggerating while socialists would have said that the situation was worse.
In the fifty years that have passed since this book was published, Canada has changed. The WASPs in Canada have merged with the Canadians of Central and Southern European descent Canadians of Asian descent are in the process of disappearing into the same melting pot. Canada is still far from perfect but it is unquestionably a more inclusive and open society than it was in 1960. The Vertical Mosaic however still has value for the thoroughness with which it describes what once was.