Raised in Upper Darby and along the coast of Maine, Furth has worked as King's assistant for over five years. She is credited as having illustrated the maps that appear in the novel The Dark Tower. Furth plotted the comic book spin-off miniseries The Gunslinger Born, which serves as a counterpart to the series of novels written by Stephen King. She is also credited as a writer for Legion of Monsters: Satana #1 and as an editor and creative consultant for the Dark Tower: Gunslinger's Guidebook, both published by Marvel Publishing, Inc. In October 2009, Del Rey Comics published The Talisman #0, with Furth credited as writer. This comic book series is an adaptation of the Stephen King/Peter Straub novel of the same name.