Novels can be classified into dozens of genres, and novels may belong to several of these categories at the same time. Distinctions among genres can be drawn in many ways. Such distinctions include the form in which the works are written, such as epistolary novels, which take the form of letters written between characters; the settings, such as regional novels, which focus on life in a certain area; and the purpose, such as propaganda novels, which try to convince the reader to adopt a certain point of view. Other examples of distinct forms include picaresque novels, which describe the adventures of rogues; Gothic novels, which describe ghosts and other elements of the supernatural; science-fiction novels, which portray other worlds or other possibilities for our world; and detective stories, which focus on mysteries. A few broad genres of the novel reflect some general tendencies. Social novels tend to focus on the outward behavior of characters and how other characters react. Psychological novels explore the inner workings of an individual’s mind. Education novels recount a person’s development as an individual. Philosophical novels provide a platform for authors to explore intellectual or philosophical questions. Popular novels usually involve adventure, intrigue, or mystery and appeal to a wide range of people. Experimental novels are works in which writers make major innovations in form and style.