A 1939 copy of "Superman" No. 1 has become the world's most expensive comic book after being auctioned for a super-heroic $9.12 million.

The pristine copy of Superman No 1, the character’s first solo title from 1939, was discovered in an attic in California last year

Three brothers had discovered the rare Superman comic in pristine condition under a stack of newspapers in their late mother's attic.

A 1939 copy of "Superman" No. 1 has become the world's most expensive comic book after being auctioned for a super-heroic $9.12 million.