This advertisement for Detective Comics No. 27, the debut of Batman, was featured in Action Comics No. 12 in 1939. The character grew so popular that one year later he got his own title.
Girls like a boy in a cape.
I just find it interesting that Action sold DC ad space. I mean, I guess, thinking about it, like, why not? They probably weren’t worried about competition, and comics likely still felt like a who-knows-where-this-is-going gambit. Action ruled the roost with Superman, basically starting it all. Originally just to move toy catalogs, novelty companies would include little gimicky “Adventures Of ___” strips to entice boys to pick up the next catalog and beg their Depression era single mothers to buy them all the lovely needful things inside.
For an actual factual account of all this, try something like The Power of Comics: History, Form and Culture. But my heart belongs to the historically accurate (mainly) work of fiction, Adventures of Kavalier and Clay, by Michael Chabon. Oh, and Steranko’s History of Comics (foreword by Fellini). I’ll try to schedule something for later today to prove how rad Steranko is. Let them blow ya mind.