C.S. Lewis’s surname was Lewis; he published under the initials of his given names, Clive Staples, followed by his family name. His full legal name was Clive Staples Lewis, so the initials did not replace a different surname or represent a pseudonym in the usual sense.
Lewis published some early poetry under the name Clive Hamilton. Spirits in Bondage appeared in 1919 under that pseudonym, and Dymer followed in 1926 under the same name. He later became widely known as C.S. Lewis for both his scholarly books and his works of Christian apologetics and fiction.
Readers sometimes confuse “Staples” with Lewis’s surname because it appears between the given name and family name. Staples was a family name inherited through his mother’s side. His brother was Warren Hamilton Lewis, whose middle name also reflected family connections.
Lewis’s use of initials was especially associated with his adult public identity. In private life, he was commonly called Jack, while bibliographies, publishers, and academic references generally use C.S. Lewis. These different forms identify the same Belfast-born writer and Oxford scholar.