I learn only dead languages. The "living" ones are way too boring. If you try to learn any language that is still being spoken, you will end up in the mud of phrases like "Where is the train station?" or "How much does this ticket cost?" But in Latin, you get sentences like "And many were killed or wounded, before they could have spotted the hidden foe." Much more dramatic .
(And then there are the awesome pieces of Sanskrit wisdom. I used to encounter at least one bit each week. Sentences like "Whoever mounts a tiger, a donkey, a camel, and/or a buffalo, will certainly die within six months" always had me laughing hard. (By the way, all the animals are a single composite, so it's actually not at all clear if you need to mount all four, or only one in order to die.))
And thanks for the book recommendations. I don't think I saw language playing any greater role in any novel that I read, and having that as a central piece of the plot is something I would very much appreciate. I'll need to have a look at them.