of paperback books available at this time shows no consensus on standardization of any feature; each early company was attempting to distinguish itself from its competitors.

"[2] The first four books did not feature maps on the back cover; this began with Dell #5, Four Frightened Women by George Harmon Coxe.

(A later re-issue of Dell #4, The American Gun Mystery by Ellery Queen, added a map.)

The map was meant as an aid to the reader, to show the location of the principal activity of the novel.

[4] The novels in the mapback series were primarily mysteries/detective fiction but ran the gamut from romances (Self-Made Woman by Faith Baldwin, #163) to science fiction (The First Men in the Moon by H. G. Wells, #201), war books (I Was a Nazi Flyer by Gottfried Leske, #21 and Eisenhower Was My Boss by Kay Summersby, #286), many Westerns (Gunsmoke and Trail Dust by Bliss Lomax, #271), joke books (Liberty Laughs, Cavanah & Weir, #38) and even crossword puzzles (Second Dell Book of Crossword Puzzles, ed.

There were a few movie tie-in editions (The Harvey Girls by Samuel Hopkins Adams, #130, and Rope as by Alfred Hitchcock, #262) and the occasional attempt at more artistic non-genre fiction (To a God Unknown by John Steinbeck, #407).

Novels which are today long forgotten, by largely unknown authors (Death Wears a White Gardenia, by Zelda Popkin, #13) are in the same series as valuable original paperback editions of famous authors (A Man Called Spade, by Dashiell Hammett, #90).

"[3] In the early 1950s, as series numbering reached the 400s, Dell began updating the appearance of its books.

The Ten Cent Books, 36 in all, were thin, paperback-sized editions containing a single short story told in only 64 pages (advertised as "too short for popular reprint at a higher price"), such as Robert A. Heinlein's Universe (1951).

Dell First Editions included novels by John D. MacDonald, Fredric Brown, Jim Thompson, Elmore Leonard and Charles Williams.