In this morning's LA Times, Jeff VanderMeer celebrates the end of a long wait:
Martin's love for sophisticated, deeply strange fantasy permeates "Dance" like a phantasmagorical fever dream. Bran's arrival at the crow's sanctuary contains some of the wildest, most beautifully alien scenes in the series. Even Tyrion's journey in a boat sailing down a haunted river, replete with ghost boats and thick fog, provides thrills for jaded readers: "The drowned city was all around them. A half-seen shape flapped by overhead, pale leathery wings beating at the fog.") Martin's brilliance in evoking atmosphere through description is an enduring hallmark of his fiction, the settings much more than just props on a painted stage.
The Song of Ice and Fire novels work so well because the epic fantasy is grounded in a strong horror element and because Martin skillfully conveys the gritty (often bawdy) physicality of the world while moving, with equal effectiveness, between various levels of society. Martin also owes a debt to the dark yet humane cynicism of writers like Jack Vance, even though he cares much more about the inner life of his characters than Vance. Martin's devotion to fully inhabiting his characters, for better or worse, creates the unstoppable momentum in his novels and contains an implied criticism of Tolkien's moral simplicity.
UPDATE: Just saw Lev Grossman's review in Time. He makes a couple of connections I wouldn't have:
Martin will never win a Pulitzer or a National Book Award, but his skill as a crafter of narrative exceeds that of almost any literary novelist writing today. Throughout the book I was reminded of Jennifer Egan's A Visit from the Goon Squad (which did win a Pulitzer), as well as Anthony Powell's (similarly floridly titled) A Dance to the Music of Time. But even Powell can't twist a plot like Martin. A Dance with Dragons is a big book, topping out at 1,016 pages, but it turns on a dime. Reading a novel is a little like commanding a battle: you're always reconnoitering, trying to guess where the author will go next, what's a feint and where the action is really heading. I don't know when I have ever been as comprehensively and pleasurably outgeneraled as I am when I read Martin. He raises and raises the stakes, long past when any other writer would have walked away from the table, and just when you think he's done, he goes all in. There is, apparently, no piece he will not sacrifice, no character that you (and one suspects, he) love so much that he will not orchestrate that character's doom.