Curious, would you consider a character's true first appearance in a book or pulp as their first appearance? Or does it have to be drawn along with the story - not just cover art. Conan and the Shadow come to mind as possibilities...
A pulp or book is a different animal than a comic book story, so no. And when you get right down to it, comic magazines are just larger format comic books. Look at Marvel Preview, or Epic Illustrated, for example. They are comic books only bigger. Not to mention that comic book publishers referred to their comics are "Comic Magazines" for decades. When you take that into account, the distinction between comic "book" and comic "magazine" seems even less important. Less important to me anyway. I know some will not agree with that.
for some reason Marvel started putting this at the top of the front cover of their flagship title back in November of 1961...