YA novelist Melissa Marr has inked a deal with HarperCollins for a trilogy about “a girl assassin, a demon with a soul, and a world where myth and science meet.” Publication is tentatively scheduled for fall 2013.

Marr (pictured) hit bestseller lists in 2007 with her debut novel, Wicked Lovely. The popular series will conclude in February 2011 with its fifth book. Writer’s House agent Merrilee Heifetz negotiated the deal with Wicked Lovely editor Anne Hoppe.

HarperCollins Children’s Books president Susan Katz had this statement: “We’ve been consistently impressed by the tidal wave of support for her books and the innovative ways Melissa has engaged and broadened her readership, capitalizing upon her online savvy and traditional networking efforts.”

Editor’s note: An earlier version of this post misidentified the deal.