When you contact a smaller, specialized publisher, you will often get through to the top person. The editor or publisher will know what you are talking about and they are usually very helpful. They will be able to tell you instantly whether the proposed book will fit into their line. Another way to match your manuscript to the publisher is to see the listings of appropriate acquisition editors in Literary Market Place but remember that LMP lists larger publishers not all of them. Then you will have someone to send your work to.
Many publishers prefer to have manuscripts filtered through agents.
In this case, you must match your manuscript to the agent because they specialize too. See the various agent directories and ask other writers. Today, more and more writers are bypassing the agents and publishers to publish themselves. They are making more money, getting to press sooner and keeping control of their work. Books That Were Originally Self-Published.