Generally this a person who runs his own bookstore. Some are specialized and only trade with exclusive pieces of litterature others offer more a more popular stock.
To be a bookdealer often means that one lives a rather quite life among giant stacks of books with various topics. To expect any greater occurrences would be to hope for too much. There are of course exceptions. Especially the bookdealers that trades in elderly tomes and manuscripts may now and then experience encounters with strange and marvelous things. An odd copy of an apocryphal piece of literature can be the portal to a world beyond our own....or something worse ...a piece of sanity depriving description of the forces that threatens our world.