The beginning was very confusing - I was very confused by the descriptions of the man in the boy's life. It was quite unclear if there were one or two. About 1/4 to 1/3 of the way through the book it became clearer that there were two men visiting the boy in the house.
I thought the world building in this book was quite well done. The history behind the royal houses of Europe was well done. Perhaps simplified the politics of the time but it was conceivable that the situation could play out that way. Even with the hand waving of "and then Angelica had children and made sure they got put on the thrones of Europe." I can see how in England there would be a very strong desire to have good alliances with the Deepsmen, since they are an island. :)
I was cheering on Henry pretty much the whole time, however I found him becoming less and less likable as the book progressed. I really liked Anne, I hated that she made people think she was a simpleton when she really wasn't, but again, the realities of court are harsh. I was happy that at the end she became the ruler and was respected even though Henry went back to the sea.
All in all a good solid read. Not one I would have voluntarily chosen on my own, but that is what book clubs are for. :)