There are some problems that come with writing the sort of sweeping fantasy series that Martin is setting up. One is that when you write a story that takes place across several novels you end up publishing before the story is over. Think of the Song of Ice and Fire as one long story being published piece by piece. By doing this Martin and all other authors of long series deprive themselves of the ability to edit as they go along. They can't go back and rewrite a passage from the first book if they don't like how the series is going.
We tend to believe that Martin set out with the story complete in his mind, but obviously that's not true or it wouldn't take so long between novels. The truth is more likely he had a rough outline of what would happen, but filling in the details of that outline had ramifications for the rest of the series, ramifications that couldn't be edited out or smoothed over later on. This series began as a trilogy then moved to four novels, then five and so on, now, Martin will be lucky if he can finish it in seven or eight.
The other problem with these long series is in reviewing them. Reviewing any book in this series but the first is going to be a review of the series as a whole, which isn't even done yet. How well Dance works as a novel can't be told until the series is finished and we are able to see it's place in the whole and how all the pieces fit together. There have been quite a few reviews of this novel to date, and some even praised Dance as a great stand-alone novel. But that doesn't work at all. 'A Dance with Dragons' is not a starting point for a story, it's the mid-point to an ongoing series. You can't judge the book on it's own merits, you need to view it as the part of a larger whole that it is. That this isn't a solo novel becomes very obvious in the last few chapters, when Martin almost completely gives up on a narrative structure and begins throwing in random POV chapters for characters that only appear once, resolving some of the cliffhangers from the previous book.
It's apparent now that the outline Martin had for the first three novels was rock solid. Those clip right along and tell an exciting, well written story. A lot of that is missing in this novel, which seems to meander for long passages with nothing happening. Though while Dance doesn't have the solid structure or the swift pace of the original three books obviously Martin had some sort of plan for it. A lot of what we see here in Dragons was set up in the previous books. The amount of prophecy fulfilled in this novel alone should be proof that Martin has a plan (though more of the prophecy than I care to admit went right over my head).
The fifth (and fourth) book of this series was, by necessity, going to be a letdown. After the heady events of the third book and the sweeping changes that came about because of them the characters were scattered. The first book was concise, taking the characters from point A to point B efficiently, introducing us to this world and letting us know what Martin was about. The second book built even more on that complexity, and the third book brought it all to new heights and gave us something of a conclusion. By the start of the fourth book there were now hundreds of characters across multiple continents, few of them having any interactions with the other. The series had reached a level of complexity that few had before. Martin has admitted that 'A Feast for Crows' and Dragons were never intended to be part of the overall series, but that the intended time-jump just wasn't feasible. He needed to write the two books so he could place all the characters in position for the conclusion. The problem with Dragons is that in a thousand plus pages Martin is only able to advance each individual storyline a minuscule fraction of what he accomplished across the first three books. The reader is almost forced to ask whether that solid outline still exists and will come back to close out the series, or if Martin will do what so many other fantasy authors have done and tread water for an indefinite amount of time, generating money while he tries to figure out how to end it.
The questions then are, is Dragons the height of complexity for the series? Where does the series go from here? Has Dragons done it's job of placing all the characters where Martin needs them for the big close, or has the narrative completely gotten away from him? Has Martin made so many changes to the story in the books he's published that he can no longer write what he wants? Does he still have control over where this story is going or has he lost the thread? Many people have complained about Dance, saying nothing happens or that Martin is beginning to repeat himself. I know because I've been one of them. This novel is either the setup for the endgame of the book, or it's not.
The real merit of 'Dance with Dragons' can only be understood when the series is finished. Martin, like all epic fantasy authors, has seen fit to give us pieces of his story as he writes them. We cannot judge the value of that story until it is complete. We can speculate over what might happen. We can judge each portion of the overall story as it is published, and in doing so for the first three novels will be rewarded. 'A Feast for Crows' and 'A Dance with Dragons' are similar in that when the overall story is complete they might mark the point at which George R.R. Martin lost control of his story and it got away from him, or it might be the point at which the story reaches maximum complexity before rushing to the thrilling and planned for close. This could be simply a natural down-point for the characters and the setup for the conclusion that Martin had planned all along. Really I wish to reserve judgement on the novel until the tale is finished, because once it's done we will be able to see Dance's place within the greater structure. When reviewing the book now critics often talk about the series as a whole rather than the single book itself. When the series is done they will do the same thing, only then they'll actually understand whether it's good or not.
On a more pragmatic note I think one of the reasons that this book wasn't as polished as the others in the series (most reviews cite the repetition and the need for more editing) is due to timing. This book hit shelves seven days before the season one finale of the TV show. You can imagine if you want that the publishers delayed putting the book out until the time was right and anticipation was high. But, for a book that was closing in on a decade in the making, I find it much more likely that the book was rushed to meet that date. That Martin was still working on fine tuning this massive tome when he realized it needed to be published. I know if I were his publisher I would have told Martin to either get the book out to meet the season finale or give it up and move on. A lot of the common complaints about the novel can be chalked up to a perfectionist constantly reworking his baby, then suddenly being rushed to completion because of financial reasons (namely, getting massively rich by releasing the book on the right day).
So, yeah, this book has got problems. Nothing happens, Martin spins his wheels all over the place. He repeats himself. People had set their sights on a real sequel, not the other half of the downer that was 'A Feast for Crows.' But I think all I wrote above still stands, we can't judge this book until we're able to see its place within the whole. The merits of Dance really stand with the merits of the entire series. And while I don't see this as a book I'll ever go back and reread for fun, I'm not really willing to write it off until I see what comes next. And I'm keeping my fingers crossed.