The article addresses this to some extent.Did you notice how that list skews toward children's literature. If you pull speculative fiction out you have perhaps 2 adult novels. (adult, not in the implied sexual sense.)
it was hugely popular in the 40’s through the 60’s in the US - probably the most famous and best selling ‘personal growth’ book of all time.The one that surprises me is the Dale Carnegie thing. That's a very old self-help book. Of course, it has been revised since 1936, but that still amazes me.