I posted my comment before I read yours, but we agree on that. I like vol. 1 (I first read it as a series of separate novelettes published in The Magazine of Fantasy & Science Fiction in 1979-80 or thereabouts), but it becomes a very different work once the other characters come in (and Roland's world impinges on ours). Then it takes another leap a few volumes later when Steven King becomes a character in his own work...