Pseudonym the attempt was not entirely successful – and the two are still sometimes confused by booksellers. A pen name may be used specifically to hide the identity of the author, as in the case of exposé books about espionage or crime, or explicit erotic fiction. Some prolific authors adopt a pseudonym to disguise the extent of their published output, e.g. Stephen King writing as Richard Bachman. Co-authors may choose to publish under a collective pseudonym, e.g., P. J. Tracy and Perri O'Shaughnessy. Frederic Dannay and Manfred Lee used the name Ellery Queen as both a pen name for their collaborative
Pen name but subsequent books were written by ghost writers. For instance, many of the later books in "The Saint" adventure series were not written by Leslie Charteris, the series' originator. Similarly, "Nancy Drew" mystery books are published as though they were written by Carolyn Keene, "The Hardy Boys" books are published as the work of Franklin W. Dixon, and "The Bobbsey Twins" series are credited to Laura Lee Hope, although numerous authors have been involved in each series. Erin Hunter, author of the "Warriors" novel series, is actually a collective pen name used by authors Kate Cary, Cherith Baldry, Tui T.