Fortified wine covers a broad family of styles that share one thing in common: a spirit, usually a neutral grape brandy, added during or after fermentation to boost the alcohol content and, depending on the timing, control the sweetness too. Port remains the best-known example, ranging from lighter Ruby styles built for immediate drinking through to complex, barrel-aged Tawny expressions with real nutty depth. Sherry follows a completely different path, aged under a layer of yeast called flor that gives dry styles their distinctive tangy edge, while Madeira is famously heated during production for a uniquely oxidised character built to last for decades. Australian Muscat, Marsala, and Vin Doux Naturel round out the picture, each bringing its own regional take on the same basic idea. If Port is specifically what interests you, Portuguese Wine covers the country's other specialties, and Spanish Wine is worth a look for Sherry's origins.