I mean, you're talking about Stephen King, the master of batshit crazy. The Dark Tower is exactly what I would expect from King writing his version of epic fantasy. If you want the more coherent, well crafted story, Hyperion takes it hands down.

Dark Tower and Hyperion are two of my top three series of all time. You definitely need to read it. I recommend reading all four of the Hyperion books though. The second set are farther in the future but they really complete the story.