I have recently become more and more interested in manga. Which is completely different from comic books/graphic novels. Let me show you.
First of all, manga and comics/graphic novels have entirely different styles of art. Comic books and graphic novels reflect Western standards of art; the people, though in a cartoon-y style, have that quality to their face and clothes. That quality I can't describe, because I don't have a degree in Art History (yet). But manga has a more angular quality to the face, with more expressive emphasis on the eyes. There are other differences, as well, in scenery and such like.
They also have different tropes. Comics, in my experience, often involve superheroes, or people with superhuman abilities who save the world (or city) from evil. I realize that is a gross simplification, and anyways, done right the superhero trope can have infinite fascinating variations, and the characterization can be quite good. I admit I am mostly familiar with Superman, Batman, and others (not through reading them, but through pop culture). Again, I am not an expert on comic books by any means, and I am sure there are plenty of exceptions to these guidelines I've set out.
Graphic novels, from what I see, are often more typical novels in an image form; there's a graphic novel for Artemis Fowl, for some of James Patterson's works, and other such works. Again, I am not an expert on graphic novels. I don't read them as much. But I have come across original writing in graphic novel form (one such is Amulet by Kazu Kibuishi -- which is called a graphic novel in its Amazon review, and does not have that distinctive manga style to the artwork).
But manga is both original art/writing, and is not focused on black and white/good and evil. I've come across many on supernatural themes (Soul Eater, Black Butler, etc), but also on fantasy/sci-fi themes (Full Metal Alchemist, etc), and the characters are generally more... nuanced. There's a fascination on the shades of gray. In Black Butler, for example, Ciel Phantomhive saves Victorian London from evil... but he is cold-hearted himself, and of course his butler is a demon he summoned to help avenge the Phantomhive name. In Full Metal Alchemist, brothers Ed and Alphonse Elric travel the world looking for the sorcerer's stone... but not for idealist standards. They are looking to get their bodies back, after a horrifying and forbidden alchemical ritual to raise their mother from the dead went wrong.
(Let me state again: THESE ARE TROPES. AND I AM NOT AN EXPERT ON SAID TROPES. If you are fascinated by the intricate differences between comic books, graphic novels, and manga, then do some research yourself.)
All of that being said, I do believe manga novels are a legitimate form of media, not inferior to Western artwork, and most definitely can be a books-and-writing sort of topic. A fiction novel sort of topic. Because they are like regular novels, in the sense that they convey a story (in print) through the use of characters, dialogue, backstory, plot, and narrative. And in the same way, anime (the video form of manga novels) are definitely a sort of movie/cinematic form of media, as they do the same as books except in video, moving-picture form. The same as regular movies, only anime.
Why am I going on about this topic, you may ask? Because I keep meeting people who think anime/manga are inferior/not as good as Western "literature"/find it lowbrow entertainment/ think it's for children. And I've been watching anime, reading manga novels, and I have to say, I don't find these arguments to be true at all.
First of all, why would you compare manga and Western literature? Western literature has survived the ages, yes, but they aren't some objective marker for what is good and pure in the writing world. Western literature has generally survived by fate, luck, what-have-you. For every literary work of literature, there's a hundred good literary works that didn't survive, due to a fluke of time. And manga/anime aren't even Western; why measure them against it? What does that prove? Nothing. They stand on their own feet, and there are just as many good stories in manga/anime as you'll find in any other form of media.
Second of all, I hate the "lowbrow/inferior entertainment for the masses" argument. That is what sci-fi/fantasy is, as well -- "lowbrow." "Inferior." There are many, many good stories, with intricacies and nuances you miss because you think the work is a fluffy nothing. I hate that argument when I come across it in my favorite genre, fantasy; and I most certainly hate it in anime/manga. It's not even about you insulting my taste in bookish things. It's about your stubborn and worrying hatred of something so... random. They're books, stories -- they won't melt your brain if they aren't considered the Western-literature standard by society. Open your mind a little, and you might find something amazing waiting beneath your nose.
And third of all -- children? Really? I realize they look a little like cartoons, and cartoons are usually associated with children. But anime/manga is enjoyed by all ages. As are cartoons, and children's books, and other things associated with children (like Froot Loops). And I don't really think anime/manga is geared towards children. Take a look at Attack on Titan, if you hold the opinion manga is for children. I guarantee you won't be thinking that afterwards. Also, that argument ties back in with the other two -- a work isn't childish because it doesn't "compare" with "Western" standards. Because it's mainly composed of pictures, and not even pictures based off of Western ideals of art. They are legitimate stories, and have adult themes in them as often as YA and Adult novels do.
So. Consider some anime/manga, will you? It's a cool section of the bookstore. There are many wonderful, nuanced stories to be found.