Probably more like 3.5 stars, but it's the first book in a trilogy, and it's Robin Hobb, so I'm rounding up (for now). 
 It's the first book in a series (4 books, at least as of 2013, not sure if that wrapped it up since I haven't read them all), but it's worth noting for anyone considering reading this that it's actually the 10th book set in this world. That said, it's only tangentially related to two of the preceding trilogies and even the one that it succeeds, well, it's not so closely tied to that one that you would have to read it--in fact, most of the characters here are new, and the writing is always clear enough that I could imagine one starting with this novel and not being particularly lost. But why would you want to do that when the nine books that come before it are so good? 
 The recap in a way that is both succinct and non-spoilery-ish: long ago, humans shared the world with dragons and a long-lived race called the Elderlings. Both disappeared in a cataclysm long, long ago, leaving behind only legends, ruins, and the occasional amazing artifact. However, dragons have been rediscovered, as one has returned and seeks the return of her kind. 
 Getting just a bit into the story here, a brood of dragons emerges from their cocoons... but they are weak and deformed. As soon as the (supposedly) only remaining fully-formed adult dragon discovers the (actual) only other remaining dragon in the world, they go off and mate, leaving the deformed little dragons to the care of humans who aren't quite sure what to do with them and, whatever it is, don't quite want to do it. 
 All this happens in the Rain Wilds, an area up-river from the coast, on a river that runs dangerously acidic, and a rain forest that has its own dangers. One characteristic of this place is that people who live there gradually become "deformed" with lizard-like (or, let's be honest here, dragon-like) characteristics like scales and claws. Those born "too" deformed are commonly given up to the jungle or the river to die (or discriminated against in such a way that they almost wish they had been). 
 The story ultimately revolves around a mish-mash group that sets off up the river with the dragons in search of a mythical city once inhabited by Elderlings and dragons: Kelsingra. The dragons' "keepers" are Rain Wilders who have been more transformed than the average Rain Wilder (in other words, the undesirables), along with the captain and crew of a very special river barge, and two well-to-do Bingtowners (Bingtown being the most well-to-do city of the Rain Wilds), one of whom is a passionate amateur scholar of dragons and elderlings. 
 To be honest, there's a lot more to it than that, but I don't want to get too spoilery here. The best thing about the novel, I think, are the characters. We have a broad cast here, pretty much all of whom are, at their hearts, desperately dissatisfied with their lives, and all of whom hope to improve their lot through this expedition. They're an interesting bunch, and Hobb's characterization is, as usual, deep and affecting. 
 That said, there was something deeply unsatisfying about the novel: it didn't feel like it had a real arc, either in its plot or in its character development. I felt like it just kind of ended, like it was arbitrarily cut off, to be continued in the next volume. In fact, given that Hobb mostly writes trilogies and this series is four books, it kind of makes me wonder. But the bottom line is that it's an arbitrary point within the plot and it didn't feel like anything had been wrapped up--even provisionally, which after all is the most you'd expect after one book of a larger series--for any of the characters. It was just deeply unsatisfying. 
 That said, considering how deeply moving I've found other books Hobb has written, I have a basic trust that this will all resolve in a way that will absolutely be worth it.