Kathleen Sky (born Kathleen McKinney, August 5, 1943) is the pen name of Kathleen McKinney Goldin, an American science fiction and fantasy author.
 Her pen name is her former married name from her marriage to first husband Karl Sky.
 From 1972 to 1982 she was married to fellow author and collaborator Stephen Goldin.
Judith Lewis Herman (born 1942) is an American psychiatrist, researcher, teacher, and author who has focused on the understanding and treatment of incest and traumatic stress.
City of Glass is the third book in "The Mortal Instruments" series, an urban fantasy series set in New York written by Cassandra Clare.
 It was originally published in the United States in hardcover on March 24, 2009.
A pen name ("nom de plume", or "literary double") is a pseudonym (or, in some cases, a variant form of a real name) adopted by an author and printed on the title page or by-line of his or her works in place of their "real" name.
 A pen name may be used to make the author's name more distinctive, to disguise his or her gender, to distance an author from some or all of his or her previous works, to protect the author from retribution for his or her writings, to combine more than one author into a single author, or for any of a number of reasons related to the marketing or aesthetic presentation of the work.
 The author's name may be known only to the publisher, or may come to be common knowledge.
Colin Falconer (born 1953) is a pen name of Colin Bowles, who also uses the pen name Mark D'Abranville, an English-born Australian writer.
 Works published under the pen name include contemporary and historical thrillers, and children's books.
 Under his original name he has also published books of satirical fiction; non-fiction books about language; television and radio scripts; and many magazine articles and columns.
Jane Thayer (the pen name of Catherine Woolley, August 11, 1904 – July 23, 2005) was an American writer.
 She is known best for the book "The Puppy Who Wanted A Boy", which became the basis of a 1980s Saturday Morning cartoon series, "The Puppy's Further Adventures".
 Jane Thayer wrote 86 books for children, many of which ("The Blueberry Pie Elf" and "The Puppy Who Wanted a Boy for Christmas") have become classics.
 She was so prolific that her editor suggested she publish some of her works under a pen name.
 Thus, Catherine authored picture books under the pen name of Jane Thayer, while writing books for older children and adults under her real name.
Naphtali Lewis (14 December 1911 – 11 September 2005) was an American papyrologist who published extensively on subjects ranging from the ancient papyrus industry to government in Roman Egypt.
 He also wrote several social histories of Ptolemaic and Roman Egypt to make his research more accessible to non-specialists.
 He was married to the psychoanalyst Helen Block Lewis (1913–1987), and they had two children, John Block Lewis and Judith Lewis Herman, a physician who followed in her mother's professional footsteps.
Morishima Chūryō (森島 中良 , 1756 – December 29, 1810) was an Edo period Japanese author of popular fiction who also wrote a number of works in the field of rangaku (Western studies).
 He wrote under many pen names, including Manzōtei, Shinra Manzō (or, conventionally, Shinra Banshō), and Tenjiku Rōjin ("old man from India").
 The latter constituted an allusion to the pen name Tenjiku Rōnin ("masterless samurai from India"), used by Hiraga Gennai, to whom Chūryō was the principal literary successor.
 Chūryō co-authored several plays with Gennai early in his career, and went on to write in almost all of the many genres of popular fiction that were collectively known as gesaku.
 He also wrote kyōka, or comic waka poetry, under the pen name Taketsue no Sugaru.
 Chūryō was the younger brother of Katsuragawa Hoshū, a shogunal physician and leading scholar of rangaku.
Ramsey Dukes is the current and most well-known pen name of Lionel Snell, a contemporary English magician, publisher and author on magic and philosophy.
 He has also under the pen names Lemuel Johnston.
 Angerford and Lea, Adamai Philotunus and Per Anum Ad Astra.
 His regular satirical column "The Satanist's Diary" was published in the magazine "Aquarian Arrow" during the 1980s and early 1990s under the pen name The Hon Hugo C StJ l'Estrange and included a multitude of other pen names as contributors.
Judith Lewis (née Rumelt, born July 27, 1973), better known by her pen name Cassandra Clare, is an American author of young adult fiction, best known for her bestselling series ""The Mortal Instruments".

Question: What is the pen name of Judith Lewis, author of City of Glass?
Answer: Cassandra Clare