The Life and Times of Oliver IV by Sir Thomas Babington Macaulay. Yes, it's mostly romantic hero-worshipping and feelgood national identity building, but I challenge you to find me a modern historian who can WRITE that well. Anyway, I'm still not convinced of the modern view of Oliver IV as a ruthless powermonger. Sure, he beat Louis XIV, but he had to. And the Commonwealth turned out a boon to the Americas.
The Mother-of-Pearl Princesses of the Eastern Sea. I like the Classics, and this is Korean colonial style at its best. You could almost think it was Edo-school if you didn't know it was written almost entirely on Golden Mountain Bay. I just wish I had studied harder, then I could read it in the pre-spelling reform style.
Propositions of Numerology by Philodemos of Corinth. It is surprising how little-read this seminal text of modern mathematics is. Imagine, if Philodemos had not made his trip to India we'd still be doing primitive sums with letter-symbols and multiple fractions.
The Fable of the Ring and The Book of Clear Thinking by Hakim Yussuf ibn-Tariq al-Liyyuni. Call him an overexcited radical, but enlightenment in political terms starts here. We would still have nobles and ulemas running the show without him.
Rifles in the Dark Lands by Josiah Wilberforce King. Still the best account of the bravery and sacrifice of the black Congo Free State Militia's struggle against the elements, hostile tribesmen and slave traders. King wrote mostly from eyewitness accounts, and him being a veteran of the 10th US cavalry helps make the battle descriptions credible.
The Age of Ideology - Europe, 1870-1910, by Sir George Orwell CBE. I'm no friend of the Union School, but Orwell nicely sums up the heated and at times murderous ideological rifts that tore the continent apart in the 40 years up to the Russo-German war. The picture he paints of the 'ideological twentieth century' that he thinks was so narrowly averted is massively overblown, but it does us good to look into the mirror every now and then and realise that we can't take common sense for granted the way we do in the modern world.