Of the seven, The Drawing of the Three is my absolute favorite. Next in line is the original, and often I have to debate which I like best. They are so different in tone, it is like comparing apples and oranges. It is like trying to explain that Alien and Aliens are very different types of movies even if it is the same universe and same, ongoing story. To me the first book seems almost like literary fiction but with a real story, an actual engine in it that makes it go. We don't like Roland but we are drawn to him and care about what happens. I think everything that happens in The Drawing of the Three, the entire series in fact, pivots on our visceral reaction to the monster Roland was becoming and his betrayal in the first book. I've often debated with myself if I would enjoy The Drawing of the Three as much if I had started the series right there. There is enough in the book itself to give you the backstory of course, but I'm not certain that would have been enough emotional investment in Roland. I need to understand his obsession and dislike him (at least as much as he does himself) to truly go forward.
Roland's trip to the Tower, this one in any case, is a long, suffering road where he is reaching for redemption. However, I submit it isn't a cosmic redemption he is working towards or from some sin or arrogance in the past. The suffering in this specific cycle comes from that first betrayal, when he made the conscious choice to sacrifice an innocent. He has looked too long into the abyss and the second book brings the payback. Having read some of King's commentary on the writing of the first book, how he felt about Roland himself and what transpired, and so on, I can't help but think that Sai King also felt or channeled that metaphysical pound (hell, one hundred pounds) of flesh in retribution. I'm pretty certain had I just picked up in the second book and been told about the betrayal without experiencing it firsthand, that I would have felt different emotions watching him suffer.