There isn't a comic shop on the planet which ordered enough copies of Avenging Spider-Man #15.1. This isn't entirely due to retailers being a cowardly, superstitious lot who only order the bare minimum of titles they can guarantee sales for. Marvel solicited the book as "Coinciding with the end of Amazing Spider-Man, a look back at the greatest conflict in comics history: Spider-Man vs. Doctor Octopus!" Which implied that this was a flashback issue, recapping Spidey vs Doc Ock battles of yore.
That isn't the case at all. Avenging Spider-Man #15.1 is the epilogue to Amazing Spider-Man #700. It is also the prologue to Superior Spider-Man #1, setting up the status quo and character motivations for that title. It's a crucial part of the Spider-Man storyline, and one that got horribly underordered because no one realized just what it was going to entail. [Bleeding Cool did! – Self-Plugging Rich] It turns out retailers will order more of an event than a flashback issue, no matter how fun said flashback issue may be. People interested in reading the issue are advised to contact your Friendly Neighborhood Comic Retailer and ask them to set a copy aside
for you, because otherwise you will miss out, and a second printing is only going to hit retailers on January 30th. Avenging Spider-Man #15.1, as well as Amazing Spider-Man #700 have a release date of December 26th.