From the publisher's website
Hideouts & Hoodlums is a modification of the Swords & Wizardry rules from Mythmere Games. What the Open Game License has allowed me to do is make a game as close to the original fantasy roleplaying game as possible BUT with swords and sorcery elements expunged and replaced with elements of the Golden Age of the superhero genre, circa 1939.
From the introduction of Men and Supermen v2
INTRODUCTION: HIDEOUTS & HOODLUMS is a fantasy roleplaying game, but not the type of fantasy where sword-wielding barbarians kill hordes of orcs while robed wizards shoot fireballs at dragons. This is the fantasy world of the superhero genre. The genre created by writers like Siegel, Robinson, and Kirby is surprisingly similar to the genre of Burroughs, Tolkein, and Howard. Both are escapist fantasies of, largely, male wish fulfillment. Both are morally simple worlds of good guys and bad guys.
As I grew up, reading comic books and then taking to DUNGEONS & DRAGONS, I often wished there was a way to combine my two passions. Many game systems have come and gone in the 26 years since I started gaming that attempted to do just that, but none of them greatly resembled D&D. In time, I realized that too many superhero games were obsessed with endless customization, while part of the charm of D&D was its very limitations - its limited archetypes with their preset paths from obscure novices to powerful uber-heroes. And, while I grew up with the comic books of the ‘70s, I also came to realize that an Old School superhero game should seek to apture the feel of Old School superhero comic books as well. In both cases, I have gone as close to the original sources as copyright laws allow.
Defining moments in the development of H&H rules were when I realized that undead turning could become a mechanism for wrecking things that would give superheroes a constant ability not tied to the "fire and forget" spell method of D&D and when I realized that other superhero games have made the "mistake" of becoming bulky and unwieldy by attempting to catalog every type of superpower imaginable. As I came to realize, whether a superhero wrecks things by melting them with fire, or freezing them until they become brittle and crack is all flavor text, or breaking it with his bare hands - the actual game mechanic need only be about whether the thing was wrecked or not. I have gone back to the earliest comic books to look at, not how the superheroes did their amazing feats, but what precisely those amazing feats were.
Stripped to their essentials, the rules for a superhero game are relatively short compared to, as the introduction to the SWORDS & WIZARDRY rules puts it, "the multi-paged rule-libraries required to play most modern roleplaying games". And yet this game allows one to play a two-fisted tough guy who grows into the world’s best fighter, a tuxedo-clad stage magician who grows into master of the mystic arts, or a superhero who goes from being able to knock down doors to knocking down mountains. Also, to quote the S&W introduction again, "The customizability of a small system is very powerful (it is always easier to add rules than to untangle them away)". This will also be true of H&H, which will expand through supplements as the Golden Age of comics expanded to incorporate more ideas. New material will not come faster than a locomotive or a speeding bullet, but will hopefully be as exciting as reading about characters who are that fast.