It's a solid, straight-up adventure novel. The most interesting aspect of it is the ambiguity of Long John Silver's character: he's alternately sympathetic and menacing, and sometimes both at the same time. Aside from questions of loyalty, it's a straightforward tactical contest between the good guys and the bad guys. It's an engaging and enjoyable read, but it's definitely young adult. (I'm also currently working my way through the audio book of Captain Blood, which has more complex characters and a greater awareness of social and political issues.)