Collecting This is a DELL BOOK
Between 1942 and 1962 (according to William H. Lyles, Putting Dell on the Map) Dell Publishing Company put out 2,168 paperbacks. Their first (Dell #1) was Philip Ketchum's Death in the Library The back cover sported an eye peeking through a keyhole, and the blurb:
presenting a new exciting Mystery Series selected by the
Editors of America's Foremost Detective Magazines.
The second, third, and fourth books are pictured above, and bore the same back cover content. With Dell #5, Four Frightened Women by George Harmon Coxe, Dell decided to do something new. They included a "Scene of the Murder in 'Four Frightened Women'" on the back cover. It was a hit, and the tradition continued with a total of 577 maps, diagrams, or blueprints adorning their back covers.
(When Ellery Queen's The American Gun Mystery (Dell #4) was reprinted, a map was added to the back cover, replacing the original content).
Dell Mapbacks have fun cover art: sometimes gaudy, sometimes sexy, at times stunningly brilliant. The map on the back covers rarely adds anything but charm. (Notable exceptions are some of the more clever puzzle-mysteries such as Hake Talbot's Rim of the Pit and the mysteries of John Dickson Carr (AKA Carter Dickson). The map from Rim of the Pit pictured here was taken from sketch by the author).
Often the editors abridged the novels that they reprinted. According to Lyles, this abridgement was often pretty merciless.
On the positive side, Dell generally chose top quality mysteries to publish, with authors that included Margaret Millar, Dorothy B. Hughes, Agatha Christie, Brett Halliday, Rex Stout, as well as the aforementioned Queen, Carr, and Coxe. Dell also made it a tradition to include a list of dramatis personae, "The Persons This Mystery is About," before the title page.
The Mapbacks weren't all mysteries. There were some romance novels, adventures, science fiction novels, and some books that, if you judge by the cover, were only meant to titillate. I can't speak for the content of these books, but the covers are pretty fetching.
Below are a few interesting covers - some of them favorites of mine, others just curiosities. Note that the A.A. Fair (Erle Stanley Gardner) novel pictured below, Fools Die on Friday, was later reprinted (as Dell #1542) the woman pictured was showing considerably less skin.
Below are a bunch of the back cover maps. Feel free to click on them for a closer look.
This is a DELL BOOK