While it is often easy to give a physical description to most characters in a novel, this often requires a second look. Good authors will often use this as a way of telling the reader so much more. Getting a picture in the readers head of what a character looks like is important, but giving the reader an insight into their soul is a totally different skill.
Still, every reader will come away with a different image of what the character looks like and what kind of person they really are. This is not necessarily a bad thing, since it helps all readers relate to a story on a more personal level. It is important, however, for any misconceptions to be avoided, if possible.