For I need not remind such an audience as this that the neat sorting out of books into age-groups, so dear to publishers, has only a very sketchy relation with the habits of any real readers. Those of us who are blamed when old for reading childish books were blamed when children for reading books too old for us. No reader worth his salt trots along in obedience to a time-table.
It is usually unbearably painful to read a book by an author who knows way less than you do, unless the book is a novel.