Published in 1935, the Secret Museum is a mystery book. It has no author or credits, no copyright, no date, no page numbers, no index. Published by "Manhattan House" and sold by "Metro Publications", both of New York, its "Five Volumes in One" was pure hype: it had never been released in any other form.

Advertised as "World's Greatest Collection of Strange & Secret Photographs" and marketed mainly to overheated adolescents (see the 1942 Keen ad, left), it consists of nothing but photos and captions with no further exposition. This was not a book published to educate (despite appearing on some public library's shelves), but to titillate (literally)— it's emphasis was on the female form ("Female Beauty Round the World") and fashion, and it featured as many National-Geographic-style native breasts as possible. But anything lurid, weird, or just plain unusual is fair game. This was a book to gawk at by flashlight under the bedcovers.

The Secret Museum is organized into five "albums" (America, Africa, Asia, Europe and Oceania), but within those areas it's a jumble with no order, laid out to fit as many photos as possible per page. Strangely, there isn't a single photo from the United States— it skips from Mexico north to Canada as if nothing were in between.

The photos themselves range in quality from fair to atrocious, with almost all being bad or very bad. Grainy, damaged, and either too-low or too-high contrast, they appear to have been copied from scratchy, abused tomes such as Hammerton's Peoples of All Nations (1922), Johnston and Guest's The World of To-Day (1907) and others, without attribution.

The tone of the commentary is dated, and uniformly racist in the extreme, often hilariously so. It reads like the patter of a carnival sideshow barker, from a time when the world was divided between "modern" Europeans and "savages". The photos were taken from the 1890s through the early 1930s, with period commentary to match. This was the era of eugenics ("the self-direction of human evolution") before it acquired a terminal taint thanks to Nazi Germany.