Many YA writers were established in other genres before venturing into YA, but used pseudonyms. An adult romance author, for example, would clearly want to distance herself from horror novels aimed at teenagers, and could adopt a different pen name to do so. Sometimes, the reasons behind pseudonyms aren't so obvious.
Nicholas Adams is a curious case. It's actually a pen name that was created by Daniel Weiss Associates that was used by several authors to write teen thrillers during the 90's.
Clay Coleman was the first author to use the pen name, in 1990, to kick off a series for HarperPrism, with the novel Mr. Popularity. The series, Horror High, would continue for several volumes and would cite "in the tradition of R.L. Stine" to entice readers (that, and a $1.99 special introductory price). The series followed students from Cresswell High School as they tried to avoid being murdered by various killers. Clay Coleman would continue to write Horror High novels for four additional installments, the books published at a rapid monthly pace, before his run ended with Sudden Death, whereupon other authors took over. Bruce Fretts wrote Sudden Death (Horror High #6), Debra Doyle and James D. MacDonald wrote Pep Rally (Horror High #7) and Sherwood Smith wrote Final Curtain (Horror High #8) in 1991, whereupon the series would take a three year hiatus before returning in 1994. Later books donning the Nicholas Adams name would cite Horror High as a bestselling series, so they were very successful. When Horror High returned to bookstore shelves three years after "Nicholas Adams" ended his run, it was taken up by Nigel Robinson, who would pen seven more books in the series, beginning with Symphony of Terror in 1994.
Most of these authors had success outside of Horror High, where they dropped the Nicholas Adams pseudonym, with perhaps the exception of Bruce Fretts, who I can not find any other listing for. Clay Coleman wrote six books in the Escape From Lost Island series between 1990 and 1991. Debra Doyle and James D. MacDonald have written many fantasies and mysteries and won the Mythopoeic Fantasy Award for Children's Literature in 1992 for Knight's Wyrd. And Sherwood Smith has had plenty of success in the fantasy genre, writing for Fantasy Realm Magazine, as well as various series, such as Exordium, a continuation of L. Frank Baum's Oz series, and the Wren books. Smith's "Mom and Dad at the Home Front" was a finalist for the Nebula Award for Best Short Story.
Debra Doyle and James D. MacDonald would also write more YA in the form of the werewolf book Bad Blood in 1994. They would publish two other books in the series over the next year, through Berkley. They would return to HarperPrism and the Nicholas Adams pen name for one final novel, 1994's Vampire's Kiss, as well as the novella Blood Brothers, which was included in the book 3 Times the Fear, alongside stories by Bebe Faas Rice and Mark Sumner.
John Peel would be the next author to take on the pen name of Nicholas Adams after Horror High, writing I.O.U. for HarperPrism in 1991. The book would be published in the U.K. as part of HarperCollins' Nightmares line, which was an attempt to compete with Scholastic's highly successful Point Horror line. I.O.U. is named a bestseller on covers of later books. Peel would go on to pen Horrorscope for the Nightmares line, while the 3 Times the Fear anthology book would be included in the line as well. Santa Claws, which John Peel wrote in 1991, would not be included in the Nightmares line.
John Peel would also go on to write several more teen thrillers as John Peel, beginning with Talon in 1993. In 1995, Peel launched a new series, beginning with Dances with Werewolves. The series, Tombstones, would only last two volumes, however. Peel has otherwise had a successful career writing novelizations for franchises such as Dr. Who, The Outer Limits and Star Trek, as well as middle grade fiction, like the Diadem: Worlds of Magic series, 2099, and installments of Are You Afraid of the Dark?
Nicholas Adams YA titles
Mr. Popularity (Horror High #1) (1990)
Resolved: You're Dead (Horror High #2) (1990)
Heartbreaker (Horror High #3) (1991)
New Kid on the Block (Horror High #4) (1991)
Hard Rock (Horror High #5) (1991)
Sudden Death (Horror High #6) (1991)
Pep Rally (Horror High #7) (1991)
Final Curtain (Horror High #8) (1991)
Santa Claws (1991)
Vampire's Kiss (1994)
Debra Doyle and James D. MacDonald YA titles
Bad Blood (Bad Blood #1) (1994)
Hunters' Moon (Bad Blood #2) (1994)
Judgment Night (Bad Blood #3) (1995)
John Peel YA titles
Talons (John Peel) (1993)
Shattered (John Peel) (1993)
Poison (John Peel) (1994)
Maniac (John Peel) (1995)
Dances with Werewolves (Tombstones #1) (John Peel) (1995)
The Last Drop (Tombstones #2) (John Peel) (1995)
Book Synopsis Samples:
Aries: Avoid confrontations. A bad day for relationships.
Soon she would come.
It was written in the stars.
Finally Jenny Warren left the protective light of the streetlamp behind. She walked fast, her shoes tapping on the sidewalk.
In the shadow of the night, the watcher smiled. His hands tightened their grip on the scarf. "You should have paid attention, Jenny," he whispered to himself.
"Didn't you read your horoscope today?"
Mr. Popularity (Horror High #1)
In the tradition of R.L. Stine, this series of novels features an anti-hero who does to an American high school what Freddie Krueger did to Elm Street.
Cassie Arthur can't believe she is actually dating Brad Forester, "Mr. Popularity." She has no way of knowing that Brad hears voices that tell him to get what he wants--at any cost.
Bad Blood (Bad Blood #1)
The moon is full tonight. And something is going hunting...
When Val Sherwood and her friends went for a hike with the Sunset Hills Ecology Club, they didn't expect to see more than the usual wildlife. But when stories told around the camp fire came true, Val had to find a way to live 'til morning.
Dances with Werewolves (Tombstones #1)
Holly Brand is a heroine! She stopped a mad werewolf in the act. Suddenly, Holly is having the time of her life and is even nominated to be Midwinter Dance Queen.
But it's not over yet.
The werewolves are coming to the dance, and she'll have to save the last one for them.