Conversation so far:
What were Georg Brandes' later writings?
Brandes wrote with great depth on the main contemporary poets and novelists of Denmark and Norway.
What were some of Georg Brandes' most important later writings?
The most important of his later works was his study of William Shakespeare (1897–1898), which was translated into English by William Archer and was highly acclaimed.

Question: What made that his most important work?
Self-contained rewrite: What made the study of William Shakespeare Georg Brandes' most important work?