Comic books are often dismissed as juvenile works, but they also represent a powerful art form that attracts imaginative storytellers who are interested in writing about the entire spectrum of human behavior - even the dirty stuff. They may not all be great, but at the intersection of graphic content, gore, and quality you'll find the best comics that definitely aren't for kids.
In the Golden Age, many comics embraced adult elements with the enthusiasm of pulp fiction. After the advent of the Comics Code Authority in 1954, this content was forced underground to small press publishers, making it harder for mature readers to find the adult storytelling they craved. It also led to a slew of comics bereft of plot and a strengthening of the perception that the only "acceptable" comics were those portraying facile, simplified superhero stories.
Despite these conditions, some of the comic world's best creators took leaps of faith and put out comics that explore explicit themes, yet aren't totally bad. In fact, these adult comic books are often masterpieces. While they aren't necessarily racy comics, these mature comic books definitely aren't for kids.
Ironwood isn't just the mystical forest between the realms of goblins and men (and other unknown quantities). It's also what will be happening in your imagination when you read Bill Willingham's racy sword and sorcery romp.
Just so you know exactly what kind of comic you're in for, in one book the protagonist is being explicitly touched by a centaur and, later on, said centaur gets taken care of by a demon with a very long tongue.
As a mainstream artist, Howard Chaykin liked to push the envelope. When he struck out on his own, the result, Black Kiss, actually had to be distributed in a sealed bag. The hard-boiled crime comic's graphic exhibits of behavior were too much for its original printer. When it finally hit comic stores, it arrived in a bag so that no one could browse the content without paying full price.
Anyone who did pay found a noir piece full of many of the fringe elements of society.
New Port City falls under the rule of the villainous Bomb Queen after she devastates all her rivals - and her clothes. With a full chest display on the loose more often than not, she dominates the news, the government, and any man she pleases.
She has a cute cat for a sidekick, but by no means is this title meant for kids, unless you think the young ones would benefit from a dose of innuendo and charred neck stumps.
Grant Morrison claims that much of the plot of The Invisibles was told to him by aliens when they got him from Katmandu. It's good to know that aliens like tantric interactions, cursing, and racy magic as much as Earthlings do. At one point, the main characters find themselves trapped inside the movie 120 Days of Sodom, which is also definitely not for kids.
When the series faced cancellation, Morrison tried to organize an event, where the energy from the simultaneous self-pleasure of all his readers would save the series. It must have worked, as he was able to complete the three-volume opus.