I wasn't really hooked. I think it was a interesting read, but I got no motivation to read further. Might have been, because I read a note from King before, that he also did no knew yet, how the tower worked. And he just wrote freely to explore it, too. So I expected the story to have even bigger holes in the plot than his ordinary books and trouble to get the story lines together in a consistent way in the end, leaving too many logic errors.
But maybe I should give the tower a second try one day.