The sources listed here offer information on the main characters that appear in various mystery and crime novel series, such as Brett Halliday's Michael Shayne, Lawrence Block's Matt Scudder, and Mickey Spillane's Mike Hammer.
Baker, Robert A., and Michael T. Nietzel. Private Eyes: One Hundred and one Knights; A Surveyof American Detective Fiction 1922-1984. PS374 Dr B34 1985x.
Bleiler, Richard J. Reference and Research Guide to Mystery and Detective Fiction. 2d ed. Ref PN3448 D4 B59 2004.
Brunsdale, Mitzi M. Icons of Mystery and Crime Dection: From Sleuths to Superheroes. 2 vols. PN3448 D4 B77 2010. Essays on famous characters and their creators, from Hercule Poirot to Jim Chee. Each chapter includes a chronology, critical analysis, list of actors portraying the character, and a comprehensive list of books, stories, plays, films, and television dramatizations, plus a bibliography for further reading.
Classic Crime Fiction. Includes a list of series characters.
DellaCava, Frances A., and Madeline H. Engel. Sleuths in Skirts: Analysis and Bibliography of Serialized Female Sleuths. PS374 D4 D46 2002. 522 adult female detectives appearing in multiple novels are covered. Each entry identifies the serialized sleuth and lists all novels in which she has appeared. The arrangement is by author. Includes a list of works cited and indices of pen names of series authors, names of sleuths,occupations of sleuths, and book titles.
Detective Fiction. This Wikipedia article contains a list of fictional detectives with links to Wikipedia articles about them.
Geherin, David. The American Private Eye; The Image in Fiction. PS374 D4 G39 1985. Covers 27 characters.
Hagen, Ordean A. Who Done It? A Guide to Detective, Mystery, and Suspense Fiction. Z5917 D5 H3. Includes a guide to characters, supplying the author and the title of the book in which they appeared.
Hubin, Allen J. Crime Fiction II: A Comprehensive Bibliography 1749-1990. Z2014 F4 H83 1994
Kramer, John E. Jr., and John E. Kramer III. College Mystery Novels: An Annotated Bibliography, Including a Guide to Professorial Series-Character Sleuths. Z1231 F4 K73 1983
List of Female Detective Characters. Wikipedia lists with links to other Wikipedia articles. Covers both movies and television.
Markowitz, Judith A. The Gay Detective Novel: Lesbian and Gay Main Characters and Themes in Mystery Fiction. PS374 H63 M37 2004. Covers 103 characters, including Katherine V. Forrest's Kate Delafield, Joseph Hansen's Dave Brandstetter, and Ellen Hart's Jane Lawless.
Nichols, Victoria, and Susan Thompson. Silk Stalkings: More Women Write of Murder. PR830 Dr N53 1998. Guide to main characters in the mystery fiction of women writers.
Randisi, Robert J., ed. First Cases: First Appearances of Classic Private Eyes. PS648 D4 F57 1997. Covers fifteen PI's.