Doc Savage is hard to place in any one publisher's pigeon-hole, which may be the reason Bantam Books reprinted the adventures with "Novel" on the spine, instead "Science Fiction" or "Fantasy". Granted many of Doc's newer fans come from the sf community, but the audience is much wider, encompassing old fans of the original magazine, and male readers of light entertainment series, like The Executioner as well as sf and fantasy readers. Why should so many different kinds of people like Savage and his five amazing aids? Quite simply, because the Savage canon crosses numerous generic borders, picking and choosing elements indiscriminately but effectively to produce the all-time greatest adventure series.
The casual reader browsing through the shelves of a used bookstore might come across many of the supersagas and think the series was science fiction. The James Bama covers often portrayed scenes as common to early sf as dinosaurs (The Land of Terror, The Awful Egg), weird machines (Murder Melody, The Spook Legion) and strange creatures (The Other World, The Sea Angel). But is it sf for all its Frankensteinian mad scientists, gadgets and super-men?
I think not. Science Fiction has about as many definitions as there are Savage novels, but predominately among the informed, the definition of true science fiction is the qualification that sf shows how a new invention, discovery, or being effects society. Granted much of early sf doesn't conform to this rule and is likewise not much read anymore. If Doc is sf, it is of the poorest variety.
The closest Doc comes to sf is in predicting future devices. Though not a primary purpose of science fiction, Lester Dent, author of the bulk of the canon, did predict such inventions as Sea-trace, radar, shark repellent, nerve gas, answering machines, the dog whistle, gas grenades, the machine pistol and black light photography. Dent accomplished this partly by imagination but also by following mechanical and engineering journals, much in the same way Jules Verne studied patents.
Though the weird gadgets of the Savage novels are certainly not the ordinary props of mainstream fiction, Kenneth Robeson(s) never show how these new discoveries effect mankind as a whole. The incidents are always localized, effecting only a small number of people, usually three or four victims, so that the powerful new weapon exists in a vaccuum and its effects disapate within a plot of action.
If the science is also not sufficient to make Doc a science fiction character, then perhaps their pseudo-nature can be described as that branch of fantasy called Science-Fantasy (including older writers like Edgar Rice Burroughs). The bulging perfect man known as Doc Savage is not too far drawn from the classic fantasy heroes, beginning with Beowulf. Like Prince of the Geats, Doc battles the superior forces of evil and wins. Thematically, the two are one. Good defeats evil. Unlike Hercules and other mythic figures, it is Beowulf that first sets one man (a superman, granted) against foes in personal combat. Hercules has his labors, but as often as not, is competing against himself rather than an advesary.
Where Doc splinters off from the traditional fantasy is in the background of Doc's world. Fantasy in general evokes another world, a fantastic realm inhabited by fantastic people. Though Doc certainly qualifies, Lester Dent strove to make Doc's New York as real as possible, a normal place where unreal things happened. In this Dionyesian way, Savage's rality is closer to modern horror or dark fantasy which places horrific monsters and events into very normal situations (sometimes referred to as a Twilight Zoner, after the television show which capitalized on this kind of story).
Many of the situations in the Robeson books are horrific: men being dissolved, captured by weird advesaries, mad men terrorizing the weak, spooks, goblins, witches and monsters. Is Doc Savage horror fiction? In this instance it is clearer from the beginning that the Doc novels differ greatly in theme. Horror fiction works by making the reader see his own life within the story, to sympathize with the characters, to wish them to survive. Though we always cheer for Doc and his companions, there is never any real fear that Doc will die, suffer terrible mutilations, or be driven insane. Doc is the perfect man. He is the antithema to horror. In a world where absolutes exist, terror falters. Only in knowing that the characters in horror fiction may or may not be killed, etc. do we become agitated. Though Monk may be on the verge of suffocating to death, Renny surrounded by poisonous snakes, we always know that Doc will win out, save them and catch the baddies. It is essentially this pattern that we expect from a Savage novel.
And it is this pattern that is reflected in mystery fiction. In a detective-type mystery the investigator plays the part of order, to find the killer and right the wrong. Doc Savage serves the same purpose. Is Doc Savage canon then a mystery series? The outward trappings of the books might convince an unwary reader, for the novels are crammed with mysterious villains, secret messages, codes and murder victims. But again, though the elements are there, scattered far and wide through the supersagas (several title begin with "Mystery": Mystery Under the Sea, The Submarine Mystery, Mystery Island, Mystery on Happy Bones), the ultimate purpose of Lester Dent and the other writers is not writing a detection puzzle. Though occasionally Doc is occupied with solving a strange incident or rumor, the stories do not, in fact, follow the five rules that delinate a mystery, the most obvious being that all the clues be placed before the reader. Doc pulls magical rabbits out of his hat time and time again.
Secondly, while the villain is often another character known to the men, the suspects are not always indicated, nor is the area of the story limited to allow the reader the fair chance of solving the crime, to do so would be counter to the point of the stories, which is to observe Doc and his amazing talents engage the problems and villains, while we sit and observe and be amazed. The spectator's role is not the active challenge of mystery fiction. Along with science fiction, the mystery genre is the one most often cannibalized in the Doc novels.
Other genres that should be mentioned are war, flying stories, Westerns and romance. The novels between 1941 and 1945 were filled with propaganda against Hitler and his allies. Though the occasional story like The Black, Black Witch are war stories (in this case Doc and Monk are trapped when a secret message asks them to cross enemy lines), the war-time atmosphere is not usually key to the events in the plot, since some sinister/weird elements accompanies it. This kind of propagandistic flavoring (lacking much accuracy or any historical value) is ultimately irrelevant and often inaccurate.
While no actual Western adventures exist for Doc, Lester Dent's experiences in panning gold in Wyoming, telegraph-work in Oklahoma, and other Western locales find their way into the books, giving them a Western flavor. The Green Eagle and The Awful Egg are set in locales traditionally part of the "horse opera" but are in essense not cowboy stories. The flying elements is much the same in the canon, though several books feature wonderful airel battles, they are not truly flying genre stories. The other genre, romance, does poorly with Doc Savage. The Man of Bronze meets many imperiled beauties and avidly amorous women, like Princess Monja in Hidalgo, but Doc spurns them all. His relationships are all with men (somewhat homosexual according to critics like Harry Harrison). Doc's love seems restricted to his father, his country and the Cause. All this should not surprise us, as the original target audience of pubescent boys would not want it any other way. When romance does occur it is with secondary characters, which Doc saves then sends on their way. Always the bridesmaid, never the bride...
So what are the Doc Savage books? First and foremost--Action! Daring escapes, evil villains, dire situations to bet the clock. The original readers of Doc Savage Magazine knew when they plunked down their hard-earned Depression Era dimes, they were in for a roller-coaster adventure, without the bleak realities of the times. Doc offered a powerful, positive Man-Against-the-Odds world, which must have been very appealing to the 1930's factory worker on the verge of unemployment. Whether a little bit of science fiction, a tad of mystery, a spicing of horror, all wrapped up in a thunder-busting cover, mattered little to the readers, as it does now. Doc is exciting reading in any era.