Where's the Line Between Fanfic and Reboot?

Today I'd like to ask all of our readers an open question. The Washington Post today proudly trumpets the publication of three new works of fiction: And Another Thing..., Dracula: The Un-Dead, and Return to the Hundred Acre Wood. All three of these books are based on the work of three very famous authors: Douglas Adams, Bram Stoker, and A.A. Milne, respectively. The new novels are written by completely new authors, using the same characters and plot devices the original authors employed.

This idea of writing new stories using another author's world as a starting point seems eerily similar to a very popular online activity: fan fiction.