Recently, I asked my readers what aids they use to visualize book characters--cover, context, or character casting by the author. The disparity in response between people who read and people who write took me by surprise.
I'm a minimalist. When I write I tend to toss in a few details here and there, but leave the actual visualization to the reader. I discovered I'm not the only writer who prefers this, but guess what? Readers want description. In the words of one lady, "Lots of it!"
Of course, I doubt that means she wants pages describing each wart and freckle, but she does want to know the character has warts and freckles. She wants a clear image of who the author has in mind, and she doesn't want it through actors' photos.
One Twitter friend let me know right fast that when the cover art doesn't match the character description it tinges her view of the entire book. She bought a book with a beautiful brunette on the cover, then discovered the character was strawberry blond. I know it's difficult to find pictures to match what the writer has in mind, but what this lady described shouldn't have happened.
To provide "lots" of character description without bogging the text, without being too apparent, and without bouncing out of POV can be a challenge. For romance writers, it shouldn't be too difficult since we're required to throw the two main characters together as soon as possible. Each one describes the other. But for authors of other genres, particularly those who write in first person, the challenge is to avoid cliche means of description--the mirror routine, the clothes selection process--unless those methods receive a face-lift, a unique twist.
Back to cover art: character depiction isn't necessary, according to some who responded--something we all know is true. What's important is that the cover is intriguing. It doesn't even have to give a good representation of what the story's about--that's what back-cover copy is for. An intriguing cover lures readers to pick up the book and read the back, flip through the pages, read a passage or two. It's one of the most valuable marketing tools out there, but it doesn't rank as one of the means for readers to visualize the characters.
They seem to want description. Lots of it.