His Majesty’s Dragon, the first novel in Naomi Novik’s Temeraire series, is a wonderful book by my standards. Captain Will Laurence is serving with honor and distinction in the British Navy, I’m guessing circa 1920, when his crew discovers a dragon egg aboard an enemy ship, and Laurence becomes the dragon’s handler once the dragon hatches.
I like the characters of Captain Harcourt, Temeraire, Lily, and Levitas.
While the book is aimed at adults who love fantasy and sci-fi, I think it'd be suitable for mature teens who can handle some violence.