well...there are certain other books you have to read of his (although I didn't re-read Insomnia, and that's another one of his I know I read but don't remember at all. He has a few...Duma Key is another.) because of their connection, so...the Gunslinger will be a slog, but the second one (The Drawing of the Three) is pretty good, and then it's a journey. Some of it I hated, because it's more pure fantasy/sci-fi/western, others I loved because it is Stephen King and he does some King stuff.
It's a fun journey! :)