I talked a bit about branding on Tuesday, but wanted to discuss it further.
To me, branding is about voice.
Yes, the art department will create a cover for your book when it is published. And hopefully all the sequels will be consistent so when your fans see a new book, they immediately identify that it's the next (insert your name here) novel.
I think of Ally Carter's Gallagher Girls and Stephenie Meyer's Twilight series as examples of great branding. You see their covers and automatically know who wrote it, without ever needing to see the name of the author.
But even more important than their cover art is the consistency of their voice. If Ally's next book was serious and depressing, I would never pick up another one of her books. Why? Because her brand is fun, exciting, interesting. Not serious, dark, disturbing. I'd feel tricked into buying something I didn't want. And whether they pick up your book at the local library or the local bookstore, the reader is buying into your story by reading that first page. They want the product they expected.
What type of brand do you want your voice to express?