I’m reading the Dark Tower series by Stephen King. I haven’t read anything by King before, and I’m enjoying it a lot. But after I had finished part 4, Wizard and Glass, I discovered this roadmap. It shows all the other books by King that have a connection to that series, but it doesn’t show how important those connections are.
So before starting Wolves of the Calla, I read Salem’s Lot. I’m glad that I did, because that story is very important for the new character, Callahan, and because Salem’s Lot would have been spoiled if I had read it later.
On the other hand, the connection between The Wastelands and The Stand (which I haven’t read, but I know some of its backstory) seems to be much less important. They travel through the world in which it happened, but there aren’t any characters from that book.
For the book I’m going to read next, Song of Susannah, the roadmap shows at least 8 other books with a connection. I’m willing to read a few of those, or even all, if it’s really that important to the story, but I don’t think it is.
So my question is, which of those books should I read to have the full backstory for The Dark Tower VI, and which should I read before because they would be seriously spoiled by that book?
(Spoilers only for the books that I’ve already read, The Dark Tower 1 -5, please.)