Carolyn Keene books in order

Carolyn Keene is a pen name, not a single author: it was created by the Stratemeyer Syndicate for the ghostwriters of the Nancy Drew Mystery Stories, which began in 1930, and was later used for the Dana Girls and Nancy Drew spin-offs.

Edward Stratemeyer conceived Nancy Drew as a girls' counterpart to his Hardy Boys and placed the series with Grosset & Dunlap of New York. The Secret of the Old Clock opened the series in 1930, one of four titles published that year. Mildred Wirt (later Mildred Wirt Benson) wrote most of the early volumes and is regarded as the principal Keene. Stratemeyer's daughter Harriet Adams later rewrote the original books, added new titles and oversaw the series until her death in 1982. Other contributors included Walter Karig, Leslie McFarlane and James Duncan Lawrence. The Dana Girls series ran under the same name from 1934 (By the Light of the Study Lamp) to 1979.

From 1959 Grosset & Dunlap revised the early books, modernising them and removing racist stereotypes; in the process Nancy's age rose from 16 to 18. In 1980 Adams took new titles to Simon & Schuster, and a court ruling left Grosset & Dunlap with the right to keep printing the original series but not to own the characters. Sales of the books are put at more than 80 million copies.

For collectors

The most valuable printings as a group are the early Grosset & Dunlap blue hardcovers with orange lettering, issued in their original jackets of the 1930s and 1940s; a jacket adds value even to a later printing. Russell H. Tandy painted the jackets of the first 26 volumes except volume 11 and designed the original silhouette logo; most of his original artwork was destroyed in a 1962 house fire, which adds to collector interest in Tandy jackets. True first printings of The Secret of the Old Clock are very hard to find, and collectors confirm a first edition (New York, Grosset & Dunlap) against a specialist reference such as Farah's Guide.