I was just rereading one of my favorite series, Naomi Novik’s Temeraire books. Horatio Hornblower with dragons about summarizes the general theme (the lead character is quite Hornblower-like), but of course the trick is in the execution, and I found the books to be very well done.
My favorites are the first, “His Majesty’s Dragon,” partly because it’s the freshest, and “Victory of Eagles,” which seemed to me have the most complex character development. You have to read the books in order, though; “Victory of Eagles” is the fifth, and there are eight in total.
My 10-year-old has also been enjoying them, although they are definitely written for adults, with adult language and grown-up themes (I hesitate to say “adult themes,” because that often means something different).
There is certainly plenty of violence (Horatio Hornblower! And dragons!), and references to sex, just because these are adult characters living adult lives; there’s nothing explicit, but some elements may be hard to understand if one doesn’t understand that adults have sex, that this has certain possible consequences, and that this was perceived in a certain way in the early 1800s.
But in any event, the themes (Horatio Hornblower! Dragons!) should have great appeal to smart kids who are looking to read grown-up stories.