I knew that. But these books credit the authors and illustrators, and Dr. Seuss’s name is nowhere on the cover, nor do they attempt to pass them off as new Dr. Seuss books.
Aw, c’mon - they clearly exist in the Seussiverse, courtesy of Audrey Geisel’s bank account: they may not claim to be written by the good Doctor, but they’re sure as hell pimping his creations. Ditto for Margaret Rey.
The Oz series was pimped out pretty heavily after L. Frank Baum’s death. His widow wrote a number of stories herself, but eventually other writers started getting in on the act.
Are you sure about his widow? I hadn’t heard or read that, even in The Annotated Wozard of Oz, which seems pretty complete on the book. After Baum’s death, it was Ruth Plumly Thompson, not Baum’s widow, wrote several continuations. Since then, there have been a few very weird attempts on Oz, especially with science fiction writers – Philip Jose Farmer’s a Barnstormer in Oz, Martin Gardner’s Oz book, and the way Heinlein worked Oz into The Number of the Beast. And then Maguire’s Wicked and Son of a Witch. But I can’t really think of most of those as sequels of the same kind as the other series discussed in this thread.
Now that I think about it, you might be right there. For some reason I thought it was his wife, but the name Ruth Plumly Thompson is ringing a bell. It’s still a case of an author’s creation being continued after his death, however.