Did you see Inception? If so (and possibly even if you didn't), then you know that in the movie, the main characters dig down into one person's dream to plant an idea that he will eventually believe to be his own. To do this, they go into a dream within a dream within a dream, and the further down they go, the more removed from the real world they risk becoming before the time they wake up. It's a good movie, both entertaining and thoughtful.
I bring this up because this book, this addition into the canon of the Dark Tower series, is a story within a story within a story, and it's easy to lose track of the overall flow of what's happening because they're all embedded this way. On the outside is the real world of the series -- Roland, Jake, Susannah, Eddie, and Oy on their travels to the Dark Tower -- but Roland tells a story of his earlier days as a gunslinger, which in turn has another story embedded within, which explains the relevance of the title. In fact, that story's title is the book's title, and makes up the bulk of the short (hey, 309 pages is pretty short for Stephen King) novel, and is effectively the heart of the entire book. Symbolism aside, it's hard to complain much about the structure, especially since King transitions the reader back into what was going on before the story broke into another one.
I guess if one wanted to complain, it would be easier to address the relevance of the book as part of the entire Dark Tower series. The stories are all asides, much like Wizard and Glass was (and, interestingly enough, this book follows that one in the chronography of the series), but this time the stories don't reveal much that hasn't already been revealed to us in other ways. And considering that the story arc has been completed, any further revelation about Roland at this point is just going to be superfluous. It's like making a ground-breaking trilogy of films and then following it up some 30 years later with another trilogy that comes before the first one, and making them dull, redundant, and obsolete. Lucas.
The two stories -- "The Skin Man" is the one that occurred in Roland's younger days, and "The Wind Through the Keyhole" is a fairy tale of sorts that his mother told him when he was a child -- are interesting and compelling, as any Stephen King story is, but neither of them feels particularly great. I have some uncertainty over whether or not "The Wind Through the Keyhole" is supposed to be fictional in Roland's world, or if it represents a real series of events from long ago, which makes me wonder if that story is somehow supposed to represent something in the world of the Dark Tower that I'm overlooking. There are references to other things that have come before or after this book in the series, so it does feel like it somehow ties in with an earlier time. But my memory for details in the other books isn't as great as it could be, so the book winds up feeling pretty random.
In the end, the story felt too much like Song of Susannah, where very little happens to move the plot forward, and the events feel more strung together than planned. For all the hype that this book received, and all the excitement it generates for fans of the series, I feel like it's ultimately going to prove to be a disappointment for most readers. The entire novel seems to be saying something about the importance of story, which I can totally get behind, and may be the reason why the book takes on the form of one story within another story within yet another story. I just find it to be a little disingenuous to advertise the book as "A Dark Tower Novel," when really it's just a couple of stories set within the world of the Dark Tower. If King wants to do that, I'm fine with it (I would be in full support of more stories set within that world without having to feature Roland and his ka-tet), but don't dupe the faithful into thinking they're going to be getting any new insights into the world of the series.