Publishing houses who have acquired a manuscript spend a good deal of time planning before the novel goes to print. The manuscript is read by an acquisitions editor, sent to a manuscript or copy editor, and may see a developmental editor. The publishers then schedule and coordinate printing, plan for release and publication, format the novel manuscript and send the manuscript back to the author for changes when necessary. Self-publishers also offer these services, but generally charge additional fees for their work editing and planning a novel.
Book publishers almost always have an art department whose responsibility lies solely in designing book covers and dust jackets. It is the responsibility of this department to make your book look good, and no book cover is printed without the approval of the book's editor. In the traditional publishing setting authors have no control over the book's cover. The publishing house determines how the book will look, whether the author approves or not. This differs greatly from the self-publishing industry where authors can pay the publishers to design their cover, or design it themselves, but always have final say over the book's appearance.
It is the responsibility of the book publisher to not only print the book once it's been planned and edited, but also to distribute the book for sale. Book publishers determine the novel's demographic and distribute the book from their warehouses to book sellers. Publishers convince bookstores to order the book to stock their shelves, restock copies that have sold out and fulfill orders for more books. Self-publishing offers a unique challenge for distribution if not for printing. Once the book is printed, self-published books must then be distributed by the author, or the author must pay the publisher to distribute the book.
In addition to planning, editing, designing, printing and distributing the book, publishers also market the book for the author. Marketing involves presenting the author and the book to larger audiences. Some marketing techniques include advanced copies, book trailers, promotions and promotional items, book posters and specially printed book stands, book tours and appearances at conferences. Marketing is a complex business and a well-marketed book will always outsell one that is not. Marketing self-published books is up to the author, though like many other services, the author can pay the publishing company an additional fee to market the work.