Do what you can do the best, what you enjoy first. Check the feedback from the market. Mate, if you wanna do comics purely for the business, I guess it's the sort of medium that will always find an audience- it all depends on how you're planning to distribute to the viewers -published, internet etc.
If you're doing books cause you like doing it, then do whatever you enjoy. But if you truely want to be successful with something, you adapt your work to also appeal to others. Thats what I reckon anyway, but it's only my opinion.
I just find that those that try to please thier own egos (not anyone Ive met in comics, but other creative fields), may find a few fans but the guys who also targets a certain mass group will always come out on top. I work with superheroes with CFCA but I've completed a script and beginning thumbnails for a comedy book because they do well too. There are people who like an easy read, with a few laughs and simple drawing. Laocorn's right. In comics and art, do what you want. The figures and feedback on the work will give you the rest. Spose it doesnt really answer your question. my point is your audience will. or to be more specific, pick your audience first, then see what that particular audience says. That's how products get developed man.
Hope a small part of my jibba jabba made sense or helped.
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