Historic books Detective Comics number 27 and Batman number one, expected to fetch $300,000 U.S. dollars each at auction.

Comicconnect.com's COO, Vincent Zurzolo explains what makes them so valuable.

SOUNDBITE: Vincent Zurzolo, COO, comicconnect.com saying (English):

"Anybody can have a Detective 27, anybody can have a Batman number one. But not everyone can have the personal file copy of Bob Kane's. It's pretty amazing."

Detective Comics 27 contains first appearances of the character Batman and Batman number one is the first issue of the Batman series.

They were part of Batman co-creator Bob Kane's personal collection, which is now up for auction.

Zurzolo says another precious item for comic book collectors is a Hulk number one issue, which could also sell for $300,000 U.S. dollars.

SOUNDBITE: Vincent Zurzolo, COO, comicconnect.com saying (English):

"What makes this comic book so valuable is that it is an extremely high grade. It's a 9.2