The Kick-Ass spinoff, which shifted more than 70,000 copies in advance, has been given a third printing by Marvel Comics to satisfy demand.
"Pre-orders for Hit-Girl #1 were over 70,000 copies, and we've completely sold out of first printing, the Noto variant and the limited edition white variant in 36 hours," Millar said.
"This is outselling even Kick-Ass and reaction has been amazing. Johnny [Romita, Jr] and I very chuffed."
Hit-Girl bridges the gap between Kick-Ass and its sequel, following the title character's efforts to train up Kick-Ass in secret.
> Read Digital Spy's interview with Mark Millar
Hit-Girl #1 is available in stores now.