I love MCP, especially the Ghost Rider ones. But that was first published in 1988, so def not the first one. Thanks for your answer!
Very cool, thanks for all the listings. We're getting earlier with All New Underground Comix #3 (1973), it looks interesting I might have to check it out.
Is this the one?! I never heard about this comic, but read this description and sounds interesting!: https://comixjoint.com/zapcomix3-1st.html. So far this one seems like the one, being published in 1968!
You're right this one might be the best selling! It's definitely one of the most iconic flip books.
Good insight, Zap #3 seems to be the earliest that we have found, that one has staples on the left side for both covers, correct?