A Steam Community Announcement has word from From Software that the multiplayer region lock has been removed from the Dark Souls: Prepare to Die Edition (thanks Eurogamer.net). The post also states this addresses a crash that could occur when opening the Book of Guilty, though several users have replied to say this problem remains. Here's word:

A nice fix is available for all players since January 19th 2015 to completely remove the infamous multiplayer region lock in Dark souls: Prepare to die edition.
This patch also fixes the crash that could occur when opening the Book of Guilty.
To update your game, simply launch it from Steam with the auto-update option on.
Are you ready to die again?