Amazon has been working to change that. They recently started a service called "Kindle Worlds" which allows a publisher with a popular property to make it possible for others to write stories set in that universe. There are currently about 30 properties in the program. More are coming.
Since the program is relatively new, only about 30 "worlds" available for you to write in. For each listed world, you'll see the guidelines that writers wanting to publish in that world must adhere to. The "World of Kurt Vonnegut" includes the following guidelines as of this writing:
- Pornography: We don't accept pornography or offensive depictions of graphic sexual acts.
- Offensive Content: We don't accept offensive content, including but not limited to racial slurs, excessively graphic or violent material, or excessive use of foul language.
- Illegal and Infringing Content: We take violations of laws and proprietary rights very seriously. It is the authors' responsibility to ensure that their content doesn't violate laws or copyright, trademark, privacy, publicity, or other rights.
- Poor Customer Experience: We don't accept books that provide a poor customer experience. Examples include poorly formatted books and books with misleading titles, cover art, or product descriptions. We reserve the right to determine whether content provides a poor customer experience.
- Excessive Use of Brands: We don't accept the excessive use of brand names or the inclusion of brand names for paid advertising or promotion.
- Crossover: No crossovers from other Worlds are permitted, meaning your work may not include elements of any copyright-protected book, movie, or other property outside of the elements of this World.
- The World does not include characters, scenes, events, themes or plots that are unique to derivative works such as books, movies and television shows based on Kurt Vonnegut’s novels, novellas, and short stories.
So if you'd always been dreaming of writing a sequel to Cat's Cradle, you have that chance as long as you write well and follow the guidelines above. In this case, though, you can't mix your existing characters with Vonnegut's because of Guideline 6.
This is an exciting opportunity for readers to see favorite characters shown in new ways, or in crossovers. It's also exciting for writers who have always wanted to write a story in one of their favorite authors' universes.