Question: Who published the series of young adult books in which "The Decision" is the 18th book?

Context paragraphs:
Roderick Townley: Roderick Townley (born June 7, 1942) is an American author of juvenile, young adult, and adult books, including books of poetry, nonfiction, and literary criticism.  He received his Ph.D. from Rutgers University, New Brunswick, and was for many years a poet and fiction writer, and for a time lived in New York City and wrote for TV Guide, The Village Voice and other publications.  In 2001, he began the Sylvie Cycle, a metafictional series about the spunky, fictional Princess Sylvie who lives her life in a book.

Bonnie Bryant: Bonnie Bryant (born in New York, New York) is an American author of children's and young adult books.  She is best known for writing the intermediate horse book series "The Saddle Club", which was published by Bantam Books from October 1988 until November 2001.

Bass Ackwards and Belly Up: Bass Ackwards and Belly Up is a young adult novel by Elizabeth Craft and Sarah Fain, published by Little, Brown in May 2006.  The novel is the first by Craft and Fain, better known as writers and co-producers for the television show "The Shield".  They shared the writing duties with Craft writing the characters of Harper and Sophie and Fain writing the characters of Kate and Becca.  The novel was nominated for a Borders Original Voices Award in 2006, in the Intermediate/Young Adult Books category.

Amber House Trilogy: The Amber House Trilogy is a series of young adult books by American author Kelly Moore and her daughters Tucker Reed and Larkin Reed.  The first book in the series, "Amber House", was published on October 1, 2012 through Arthur A. Levine Books. " Amber House" has been licensed in South America and Europe.  It was a featured title in the 2012 Scholastic Book Fair.  Its sequel, "Neverwas", was released on January 7, 2014.  Official publication dates for a third installment in the series, "Ever Shall", and a fourth and final installment, "Otherwhen", have not been announced as of early 2017.

The Decision (novel): The Decision is the 18th book in the Animorphs series, written by K.A. Applegate.  It is narrated by Ax.

Young adult fiction: Young adult fiction or young adult literature (YA) is fiction published for readers in their youth.  The age range for young adult fiction is subjective.  Some sources claim it ranges from ages 12–18, while authors and readers of "young teen novels" often define it as written for those aged 15 to the early 20s.  The terms young adult novel, juvenile novel, teenage fiction, young adult book, etc., refer to the works in this category.

Animorphs: Animorphs is a science fantasy series of young adult books written by Katherine Applegate and her husband Michael Grant, writing together under the name K. A. Applegate, and published by Scholastic.  It is told in first person, with all six main characters taking turns narrating the books through their own perspectives.  Horror, war, dehumanization, sanity, morality, innocence, leadership, freedom and growing up are the core themes of the series.

Johnny Mackintosh and the Spirit of London: Johnny Mackintosh and the Spirit of London is the first novel in a series of young adult books written by Keith Mansfield and published by Quercus.  The book opens on the thirteenth birthday of the title character and is written entirely from Johnny Mackintosh’s point of view.

Will Hobbs: Will Hobbs is the author of nineteen novels for upper elementary, middle school and young adult readers, as well as two picture book stories.  Hobbs credits his sense of audience to his fourteen years of teaching reading and English in southwest Colorado.  When he turned to writing, he set his stories mostly in wild places he knew from firsthand experience.  Hobbs has said he wants to “take young people into the outdoors and engage their sense of wonder.”  "Bearstone", his second novel, gained national attention when it took the place of "Where the Red Fern Grows" as the unabridged novel in Prentice-Hall’s 7th grade literature anthology.  "Downriver" and "Far North" were selected by the American Library Association for its list of the 100 Best Young Adult Books of the 20th century.  As of 2016, all twenty-one of Hobbs’ books are in print, and all the novels are available in unabridged audio editions.

Mika Launis: Mika Launis (born 1949) is a Finnish illustrator and graphic designer who studied graphic design at the University of Art and Design in Helsinki.  For his final project, he did the illustrations for a children's book written in Northern Sámi.  Launis has illustrated several books, mainly children's books.  In addition, he has provided illustrations for book covers, of which his most well-known are probably the covers of the Finnish versions of the Harry Potter books.  Some of his works have also been published as postage stamps. Launis was the 1997 recipient of the Rudolf Koivu Award, which is awarded to illustrations in children's and young adult books.  Furthermore, he won the competition to design Finland's first Euro postage stamp.

Supporting paragraphs: The Decision (novel) Animorphs
Answer: Scholastic