I need to revisit The Dark Tower, I last read it when it was incomplete and have never read it through. Very different to his more famous works. Thanks for the reminder.
Depending on where you stopped, I feel like it is gets a little bit odd in the middle but it is very much worth reading to the end.
There's also The Wind Through the Keyhole which slots inbetween the main books. Learning about this one is that made me read the whole series again only a few weeks ago. It's still as good as it ever was!
Not worth reading to the end at all. King didn't even think of a proper ending, prefacing it with a suggestion to stop reading before it. The series got weaker and weaker after second book.