A gift for a 15 year old boy who’s just told me “Napoleon was the best strategist in the whole of history”

I’ve always bought my nephew books as gifts but it’s getting harder as he gets older! He’s fascinated with history and when I asked him for Christmas gift ideas he said he loves the Napoleonic era and how Napoleon could finish wars in days. He also loves studying law and ethics. What could fit that brief? UK based if that makes any difference.