People are laughing at the SpiceDao for spending $3.8 million on a book. But one thing has shown is a group of fans of a story can get money together to spend on that story. And this can be organised in a decentralised way. We don't need Disney to buy franchises, fans can do that now.
The stories that are most undervalued in monetary terms compared to how much fans value them are probably
1. Young Adult stories as people who read these at a formative time find them really important but traditional publishers don't.
2. Sci-fi and Fantasy books as these are generally seen as less prestigious than standard literature
3. Non English Language stories.
4. Books that are out of print as that can change who owns the rights or at least makes them cheaper.
5. One from a few decades ago so the fans are now old enough to have some spare money.
6. Choose your own adventure and adventure games are eve further out of mainstream critical valuation. Comics have been mined for IP value but they are such a rich and diverse medium I am sure some areas have been ignored.
Fans of a non english language YA sci-fi/fantasy series could for much less than $3.8 million get the IP rights to a story like this. Frequently the author will have the IP rights themselves and they could well be easier to deal with than a publishing company.
I would guess once you have the rights the order of things to get the story more popular are
1. Republish the story on kindle. Effectively free. Give the author a lot of any money this earns so it is in their interests to encourage the steps below and to sell you the IP rights cheaply.
2. Set up a fan site including forums and fan fiction. Not expensive but it would take up some time with moderation.
3. Create a prize for fan art including images, fashion designs and comics and for fan fiction stories. Again this is very cheap.
If the original language can create enough interest in the franchise to keep these busy
4. Publish special editions of the book. With a new introduction, cover based on a prize winner etc.
5. Translate the story. A high quality book translation is pretty cheap. Especially if you are not under strict time pressure. Cost 5-15k per language.
6. Copy steps 1->4 in the newly translated language.
After the first franchise you carried this out on you can reuse the website software etc. I would guess each additional franchise would cost under 50k to buy and do these steps with. Even if it was 100k that would still be 38 different franchises resurrected for the price the spiceDAO paid for the physical copy of a book.
And if any one of them really succeeds and becomes popular enough to spawn a movie a large profit could be made. But thinking about the worlds of fans I think just seeing their favorite characters again either back in print for a new generation, back with new adventures in a new series of books is really what most fans want.