Ghost of the Hardy Boys by Leslie McFarlane (Methuen, 1976) - autobiography of the first Ghostwriter. 

The Secret of the Hardy Boys: Leslie McFarlane and the Stratemeyer Syndicate (Ohio University Press, 2004) - biography of McFarlane by Marilyn Greenwald. 

Hardy and Hardy Investigations by Tony Carpentieri and Paul Mular (Synsine Press, Fourth Edition June 2001) 

The Lost Hardys: A Concordance by Robert Crawford (Synsine Press, Third Printing November 1998) 

The Mysterious Case of Nancy Drew and the Hardy Boys, by Carole Kismarick and Marvin Heiferman (Simon & Schuster, 1998) 

Who Wrote That? Edward Stratemeyer: Creator of the Hardy Boys and Nancy Drew (Chelsea House, 2004) - simple biography of Stratemeyer 

The Secret of the Stratemeyer Syndicate by Carol Billman (1986; Publisher Unknown) 

Edward Stratemeyer and the Stratemeyer Syndicate by Deidre Johnson (Date Unknown; Twain Publishers) 

Stratemeyer Pseudonyms and Series Books by Deidre Johnson (Date Unknown; Greenwood Press) 

To locate reference books out of print, you may wish to post a want ad in the Bayport Gazette classifieds, or post on various e-groups.