It's certainly not light fiction, but it does involve some history of Mexican/South American aboriginals - the best book I've ever encountered about Latin America is called Born in Blood and Fire, by Chasteen. Works as a class text because it's comprehensive, but so entertaining and full of broad scope history AND the great anecdotal and weird stories that make the scope mean something, and hits just about every Latin American nation really well (although Paraguay is sadly neglected).

Maybe not right for this birthday, but next time he's ready for another thinky one? It's not too heavy (metaphorically or literally) for travelling, though ... I took it with me on my last trip (South America) and read it on trains, buses, and in the park.