They have endured. I believe Mrs. Blyton passed away in 1968, and yet there I was reading The Famous Five adventures to my boys in the 1990s (and may yet read them to my grandchildren).I devoured her books when I was little.
It used to behoove me to finish a chapter with a cliffhanger ending and say "The End!"
Not to be fooled, they would reply "No, because the last chapter is always called 'All's Well That Ends Well'!"
Busted!