Many famous authors have written under names other than their given ones, among them Mark Twain (born Samuel Clemens), Lewis Carroll (Charles Dodgson), George Eliot (Mary Ann Evans), George Sand (Amandine Dupin), George Orwell (Eric Arthur Blair), and Voltaire (Francoise-Marie Arouet). Ellery Queen is actually the pen name of two cousins: Frederic Dannay and Manfred B. Lee. Even William Shakespeare is believed by many to have been a nom de plume, perhaps for Edward de Vere, the 17th Earl of Oxford.
There are lots of reasons for choosing to appear as someone else in print. In earlier times, female writers such as Sand and Eliot used men’s names because of the prejudice against women. The Bronte sisters––Anne, Charlotte, and Emily––posed as the brothers Acton, Currer, and Ellis Bell respectively. Anne Rice, on the other hand, was originally given her father’s name, Howard Allen O’Brian, and decided when she started school to call herself by a female name.
Others opted for pseudonyms because their birth names were unwieldy, such as Joseph Conrad (né Jozef Teodor Nalecz Konrad Korzeniowski), or because they wanted something catchier, such as Mickey Spillane (Frank Morrison).
Many authors––especially genre writers––use pseudonyms, either to add color or to conceal their true identities. Because publishers of literary fiction tend to look down their intellectual noses at romance books, writers who pen romance novels frequently do so under names other than their real ones. Authors who write various types of books may write fiction under one name and nonfiction under another, to prevent confusion. Writers of erotica often use fictitious names to avoid static from employers, family members, etc.
It’s perfectly legal to call yourself whatever you wish, so long as you don’t do it for purposes of fraud. Publishers will respect your right to remain anonymous (although if you get rich and famous, information sleuths might figure out who’s really behind that notable non de plume). And yes, you can copyright your book under your pseudonym. However, if you ever try to make a claim against someone for copyright infringement, you might have difficulty proving your ownership. If you seriously want to protect your identity, don’t include your real name on records you file with the U.S. Copyright Office as that information will be available on the Internet.