I keep seeing people recommend things like 'The Sorrow of War' or 'The Quiet American', which are fine, but if you want culture you need the stuff that feels like daily life. For that, 'The Tale of Kieu' is the absolute bedrock. It's the national epic poem, and references to it are everywhere in conversation, music, even street names. You won't get the proverbs or the mindset without at least knowing its story. Then, for the modern scramble, I'd say 'Catfish and Mandala' by Andrew X. Pham. It's a travelogue by a Vietnamese-American guy cycling through the country, and it gets into the awkward, beautiful clashes between diaspora and homeland perspectives in a way history books never could. It's messy and personal, which is what culture often is.
Also, don't sleep on contemporary fiction from Vietnamese authors publishing now. 'The Mountains Sing' by Nguyễn Phan Quế Mai is a multi-generational family saga that shows how war ripples through ordinary people's rituals, food, and superstitions across decades. It’s accessible but deeply rooted. For a totally different angle, 'Dumb Luck' by Vũ Trọng Phụng is a savage satire of 1930s Hanoi under colonialism, poking fun at the rush to adopt French manners. It’s hilarious and shows how Vietnamese people have always negotiated foreign influence with a sharp, critical eye. Honestly, pairing an ancient poem with a modern satire gives you more cultural insight than a dozen dry academic texts.