Nancy Drew: Girl Detective is a 2004–2012 book series which replaced the long-running Nancy Drew mystery series. This new series is written in first person narration, from Nancy's point of view, and features updated versions of the main Nancy Drew characters. New secondary characters are introduced to populate River Heights and appear over multiple books, adding a framework to Nancy's world.

Though this series had some improvements over the Nancy Drew Mystery Stories, the drastic change in the main characters' personalities was hard for many readers to accept. The series was negatively reviewed by many fans of the series, mainly over the change in Nancy's character. In 2008, the series was changed into a trilogy format, which gained even more negative reviews than before. Simon & Schuster cut back to 4 books a year in 2010, before low sales finally forced the cancellation of the Girl Detective series in 2011. In 2013, the Nancy Drew Diaries series was launched as the replacement for Girl Detective.

In the 90s and early 2000s, sales of the Nancy Drew novel series began to drop. At a Nancy Drew conference held in early 2005 in New York, a Simon and Schuster representative said that the digests had been selling about 30,000 copies. In order to boost sales, the original series was ended and the Nancy Drew series re-launched.

This new incarnation of Nancy Drew was initially supervised by Bonnie Bryant (Jacobson), with three ghost writers writing the initial six books. The first volume of the new series, Without a Trace, reached the New York Times bestseller list in the Children's Series category and #113 on USA Today's Top 150 sellers list due to the .99 cents introductory price.

The publisher describes the series in the following way:

Nancy Drew has a new spring in her step. And it's no wonder: We've given her whole world more oomph. In the all-new Nancy Drew, we've enhanced and expanded everything you've loved about Nancy, Bess, and George, and the rest of Nancy's crew. You loved the series before, but with more dimension, you'll love the series even more now! Learn why River Heights is such a hotbed of criminal activity, meet some new key sources of information for Nancy on all her cases, become acquainted with Nancy's new nemesis, and become even closer friends with Bess and George. And that's just the beginning ...

Nancy Drew in this version is a less than perfect teenage girl prone to forgetfulness, an object of jokes, and interested in other subjects over mysteries. Bess Marvin has gained skills in mechanics and computers and is no longer slightly overweight, and described as fashionable and trendy. George Fayne has become moody and sloppily dressed in this series, always more interested in tech and sarcastic retorts than solving mysteries. Bess and George also gain siblings and family members with careers. Ned now lives in River Heights, working part-time for his father's newspaper The River Heights Bugle.

The Nancy Drew: Girl Detective novels are usually based in the fictional town of River Heights, which is located in Illinois. Other fictional cities that are mentioned are Silver Creek, East Bank, Cutler Falls, and Trib Falls, which are all near River Heights and the Muskoka River. River Heights is a 1-hour drive west of the real city, Chicago, which has been mentioned frequently.