Book editing companies ordinarily are engaged in the writing industry, constantly trying to find the right bond between a writer and proofreader.
Such a company would consist of a group of editors who work together to ensure proofreading and related services are provided to their clients within a reasonable time frame. You can also get knowledge of custom book design through various online sources.
Sometimes the companies also consist of some professional writers who may give ghostwriting services and editing services when called upon. Who better to go through your manuscript than a writer who has been there done that?
In order to market themselves well, Book editing companies constantly need to present their interest in the particular genre, their awareness of the writer's taste and style, and knowledge of the subject matter being presented for review in a manuscript format. It goes a step further than just being a company providing a service; it is one that is forced to specialize in personalizing the service for the client.
Indeed, Book editing companies are profit-making organizations and cannot be expected to be anything but. However, profit-making is not normally the driving force behind the work they do.
They are more interested in finding a good talented writer who can grow to be an exemplary writer, publishing and selling not just one, but dozens of books. The company often prefers to look towards a long-lasting relationship with a writer, not just a one-off service charged.