I've been a long-time fan of the Dark Tower series and I admit I was hugely curious to see a "middle" story pop out, long after the last book had been written. I was pleasantly surprised to find fully fleshed and embedded stories, three deep. It could have turned very complicated and burdensome, but it just worked. I really wanted to see a novel, even a 4.5 novelette, deepen and expound upon Roland's strange "more real than real" land, but while I was disappointed in that regards, what I did find were characters I really enjoyed and a "soft" exploration of the world and its honor, (or lack of). 
 It was a fairy tale (for a kid who's Pa had been gored by a shapeshifter) within a fairy tale (to pass the time while weathering a hellish storm) within a fairy tale (for us). It was by no means a series of epic tales, although it was still couched within the longer progression of the Dark Tower, so you could make the argument. 
 Could someone enjoy this book without reading the rest of the series? I think they can do so, very much. There was little enough spoilers for the rest of the tale, nor elements that needed to be built up and explored very thoroughly indeed or it loses the climatic flavor. 
 The novel was simply fun and enjoyable. :)