According to the context, I think "well-read author" means one whose work has been widely read. But dictionary definition tells that it mean one who is very knowledgeable. So is my conclusion right?
Well firstly there is a slight difference in UK and US usage of "well read". A well read American by definition is someone who has read a lot of important books. Whilst a well read Brit is someone who has learned a lot of information on different subjects by reading.
However the differences, aside, well-read author is not the same as well read author because of the hyphen. The Hyphen is used to join the two words so no misunderstanding to meaning can be made. Therefore in this case the meaning is The author has been read by many people.
Rule 5.Grammar book Never hesitate to add a hyphen if it solves a possible problem. Following are two examples of well-advised hyphens:
Confusing: Springfield has little town charm.
With hyphen: Springfield has little-town charm.
Without the hyphen, the sentence seems to say that Springfield is a dreary place. With the hyphen, little-town becomes a compound adjective, making the writer's intention clear: Springfield is a charming small town.
Confusing: She had a concealed weapons permit.
With hyphen: She had a concealed-weapons permit.
With no hyphen, we can only guess: Was the weapons permit hidden from sight, or was it a permit for concealed weapons? The hyphen makes concealed-weapons a compound adjective, so the reader knows that the writer meant a permit for concealed weapons.