It seems early, since the book is still being edited, but promotion work is already underway. Once the book is released, promotion and publicity has a hard deadline as a new release becomes yesterday's news very quickly. Although the publisher does the marketing and promotion, any additional work the author can provide can only help; after all if no one knows about your book, how can they know if they want to buy it?
My efforts are already taking effect. This blog is one of the more obvious, as is the online presence I am building. Book trailers and videos are under discussion, and the first mention of a cover was made recently which caused my ears to prick up.
I know how the book reads, but I can't wait to see how it looks.