Her debut novel, Promise Not to Tell, was published by Harper Paperbacks (an imprint of HarperCollins) in April 2007.
[1] It was released in Germany by Rowohlt Verlag, under the title Das Mädchen im Wald (The Girl in the Woods), in October 2007.
Her follow-up suspense novel, Island of Lost Girls was published by Harper Paperbacks in April 2008.
It was released in Germany by Rowohlt Verlag, under the title Die Insel der verlorenen Kinder (The Island of Lost Children); and in the Netherlands by De Boekerij under the title Het eiland van de verdwenen meisjes (The Island of Missing Girls).
McMahon also has a book of lesbian teen fiction, entitled My Tiki Girl, which was released by Dutton Children's (an imprint of Penguin Group) in May 2008.