Need help with gift for boyfriend

My 6 months with my boyfriend is coming up and I really need help finding something for him. Here’s what he likes:

Historical nonfiction. Usually some sort of philosophy guideline book. Something along the lines of a historical figure saying “I’ve lived my whole life and this is what I’ve learnt”.

One book he likes is a book written for a prince by Machiavelli. I think it’s called “the prince”.
Another one he likes is a book written for a Roman emperor. I don’t know what it’s called. I asked him about why he liked his new prince book and tried taking discrete notes.

Some things he hasn’t read yet that are also along the lines of what he likes:

There’s one by Plato, and then there’s another one by an ancient japanese swordsman that contains a bunch of life expertise.

Sorry the info isn’t very clear—I’m not a huge reader but this is my idea of what type of books he likes. Please let me know if you’ve got anything in mind that I can surprise him with.

Thank you!

by zonglydoople