It's a bird! It's a plane! It's a rare Superman…

A copy of the first Superman issue, unearthed by three brothers cleaning out their late mother's attic, netted $9.12 million this month at a Texas auction house which says it is the most expensive comic book ever sold.

The brothers discovered the comic book in a cardboard box beneath layers of brittle newspapers, dust and cobwebs in their deceased mother's San Francisco home last year, alongside a handful of other rare comics that she and her sibling had collected on the cusp of World War II.