1st appearance and origin of Captain Marvel, later renamed Shazam

1st appearance of the Wizard Shazam

1st appearance of Dr. Sivana, a scientific genius and the archenemy of Captain Marvel

1st appearance of Ibis the Invincible and Spy Smasher

1st team appearance of the Seven Deadly Enemies of Man, later renamed the Seven Deadly Sins

While not a precise swipe of Action Comics #1 artwork, this cover and other aspects of Captain Marvel led to DC (formerly National) filing a lawsuit against Fawcett for Captain Marvel too closely resembling Superman

Premiere issue of the series though the copyright notes read issue #2

There exists a very scarce Ashcan edition of this issue