This trilogy is quite different from the previous two Hobb trilogies I'd read (Farseer and Soldier's Son): it's in the third person, with about a dozen different main characters to follow around; there's certainly a wider scope this way, as well as a quicker pace, more action and less immersion in the lives of the characters. Apart from that, this trilogy is also much more consistent: where I found Farseer and Soldier's Son to start off brilliantly and then go downhill badly, this one started off okay and got better. I didn't ever love it the way I loved some previous Hobb books, but whether this is because I've gotten jaded toward her books (and their tendency toward emotional manipulation) or because she's at her best when getting deep into one character's head, I couldn't tell you. But the good news is that, unlike with the other two trilogies, I didn't hate any of the Liveship books either, so this might just be the trilogy I'd feel most comfortable recommending.
With as many main characters as these books have, the plot is complicated. Some of the threads are about characters' personal questions--one of the main characters, Althea Vestrit, spends the entire trilogy trying to reclaim her family ship--while others tell a larger story--Bingtown, the colonial city where most of the non-nautical action takes place, is facing major social changes and trying to assert its independence despite being located between two larger and more powerful neighbors. For the most part, Hobb weaves all these stories together well, although toward the end the bigger political story is sidelined in favor of the characters' personal ones. Ship of Magic begins rather slowly, with lots of long, repetitive arguments among the various members of the Vestrit family, but the plot picks up quite a bit in Mad Ship and Ship of Destiny, with more action (pirates! storms! sea battles! sea serpents!) than I'd normally expect from Hobb.
As for the characters . . . having so many of them is a double-edged sword. On the one hand, they are well-conceived, they have psychological depth and complex motivations, and they grow and change. They also all have their flaws and make mistakes. Kennit, the pirate captain who's probably the closest this trilogy has to a villain, isn't the sort of fantasy villain who entertains himself with cruelty; he's willing to do whatever it takes to get what he wants, but this is just as likely to be fighting slavery as it is murdering people. Meanwhile, Althea, who's arguably the heroine, is easy to sympathize with, but has a tendency to be selfish and dismissive of other people's feelings and contributions. We also get to know characters who normally get short shrift in fantasy: Ronica, the Vestrit matriarch, who's struggling to hold her family and their possessions together; Keffria, her daughter, who has to learn to take control of her own life back from an overbearing husband; and Malta, Keffria's daughter, who starts out a spoiled teenager but has to grow up quickly. Most of the main characters in the trilogy are women, and Hobb does an excellent job in creating in them well-rounded and realistic characters, much more relatable than the usual female fantasy characters.
The downside to having so many characters is that none of them are quite as well-developed as other Hobb protagonists, and that each reader is bound have at least one major character they find ridiculously annoying (Wintrow, in my case). Additionally, in Ship of Magic, there are a lot of rather pointless scenes with characters whose importance to the trilogy doesn't become clear until the second book (Paragon and the sea serpents in particular). Finally, in later books I found certain characters' development so dramatic as to seem a bit contrived.
Now to the story's world: Hobb does a lot here that I normally love in fantasy. We get to read about a seafaring, merchant-based society that has a 16th-century feel; there's political and social change, and an overall progressive ethos--Bingtown has to change and move forward, not return to what it was in the past; there's no ultimate evil, but rather a bunch of characters all struggling to get what they want. But while that's all good, it isn't memorable here. Hobb tends to skim over worldbuilding, a fact that's evident from her characteristically uninspired place names (the Wild Sea, Trader Bay, Shield Wall Island . . . and so on). The world feels underdescribed in a purely physical sense--rarely could I envision the places or the scenes--but beyond that, the societies are rather flat and uninteresting. I'm not convinced there are hidden depths beyond what's on the page. And there's precious little culture here: think "well-to-do merchant society" and you already know everything there is to know about the Bingtown Traders. Part of a truly compelling fantasy is a compelling, multilayered world, and despite some very good ideas, this isn't one.
As for the magic: I'm torn about that. I liked that there are no wizards here; the supernatural is (mostly) outside the characters' control. At the same time, particularly in the last book Hobb uses "destiny" to explain certain coincidences and the supernatural plays a role in a couple characters' psychology, which I wasn't thrilled about. But while I might have preferred a bit less of it, the magic fits well into the story, and it's fairly unique--living ships with talking, thinking figureheads aren't something you're likely to see anywhere else.
Ultimately, this trilogy is solid entertainment. It's a fun seafaring adventure with complex characters and some interesting concepts. With a better world, and a writing style that's more than merely serviceable, it might have been fantastic, but in the end I don't regret reading it and am glad I pushed through the first book to get to the good stuff.