(See my reviews of the earlier Dark Tower books here and here.)
Unlike in The Drawing of the Three - and indeed The Gunslinger, too, though to a lesser extent - I cannot at this moment recall, in the course of reading this book, ever being jarred out of the flow of the story by a gratuitous-seeming "horror" element (which, except for the lobster-monsters, were all of the "gross" rather than the "scary" category). I hesitate to generalize from a single book in a series of this length (especially given the ridiculous length of time over which it was written), but it is possible that the fact that this series is not, in fact, horror has finally established itself in the mind of its author.
Which is not to say it's all sunshine and roses, because, well, I'm pretty sure Stephen King doesn't do happy-fun stories. But elements of a decidedly dark nature included, the tale is shaping itself to fit quite comfortably within the fairly large borders of "fantasy". Indeed, given the scale of the quest, and of the timeline hinted at for this world's past, it is a pretty good candidate for "epic fantasy", though I know most people call it "dark fantasy". It actually reminds me a surprising amount of the Song of Ice and Fire series, wherein the world is a nasty place, people die A LOT, and yet the sense of wonder and magic in the world remains intact.
Anyway. Enough meta-discussion. In this installment, Roland and Susannah and Eddie continue along the quest for the Dark Tower, along the way battling a giant cyborg Guardian, collecting a resurrected Jake, passing through a nastily post-apocalyptic city, and embarking on a trip on a sophont, insane train with an inordinate fondness for riddles. (Given that this thumbnail sketch takes us clear to the end of the book, I suppose it could count as spoilery, but I think it's a little too, um, sketchy to be much of a problem. Also the book is nearly 20 years old.) After The Drawing of the Three I'd started to wonder if the fondness with which I remembered this series (previously read through Wizard and Glass) was the result of being youthfully indiscriminate in book-taste combined with the years of memory-fading casting a nostalgic glow over things, but it turns out this book is actually quite remarkably excellent, even from a 30-something-cynic's perspective. So, that's a pleasant discovery.
Highly recommended.