A while ago I stumbled upon an excellent excerpt/article from Peter Mendelsund’s book What We See When We Read (Vintage Original). It talks about how the best novels are often very vague about physical descriptions of their characters, leaving the reader’s imagination to subconcsiously fill in the blanks.
From the excerpt:
Good books incite us to imagine — to fill in an author’s suggestions. Without this personalized, co-creative act, you are simply told: This is your Anna.
It really got me thinking about how I describe my own physical characters. I often leave a lot to the imagination and just drop a teeny hint about their appearance every now and then, but I have to say in my current book I was a little more cognizant of how readers “fill in the blanks” after I read this piece.