Which of the following author names is a pen name, or not their actual name?
Considering Mary Shelley, Lewis Carroll, Sylvia Plath, and Albert Camus, the answer is: Lewis Carroll.
Best known for writing Alice's Adventures in Wonderland, Lewis Carroll was born in 1832 with the name Charles Lutwidge Dodgson. According to the Lewis Carroll Society of North America, Dodgson adopted his pen name in 1856 because he was modest, and wanted to maintain the privacy of his personal life.
While works written in anonymity or published under a pseudonym might feel like an anomaly, much of the history of literature comes from works without attachment to a name. It's now strange to think of Pride and Prejudice or Frankenstein without knowledge of their authors, but thus was the reality at the time of their publishing.
Publishing anonymously or under a pseudonym reached its peak around the mid-19th century. Scottish librarian Simon Halkett went so far as to compile a sort of anthology of British works – a project that eventually spanned nine volumes of stories and novels written pseudonymously or anonymously. Interestingly, most well-known British authors have been tied to an entry in its pages.
There are many reasons why authors lean toward pen names, or leaving their name out altogether. One of such reasons is Anglicization – during the 18th and 19th centuries, authors whose surnames reflected a nationality that was distinctly non-Western would change their name to better align with a British or European audience. Others, such as Theodor Giesel (perhaps better known as Dr. Seuss), changed their names to appeal to younger audiences and inspire whimsy ("Seuss" was the surname of his mother but the pronunciation was changed to rhyme with "goose" – i.e., Mother Goose).
Other authors took pen names to differentiate new works from those for which they were most famous. Among such authors is mystery writer Agatha Christie, who published romance novels as Mary Westmacott. Horror writer Stephen King even published some titles under the pseudonym Richard Bachman in an attempt to avoid the industry criticism of publishing "too many" books in one year. Once Bachman was discovered to be King himself, the author announced that Bachman had died from "cancer of the pseudonym."
Learn more about pen names and their history here.