Thesis, antithesis, synthesis

The three-route structure of Fate/stay night is the single strongest argument for the VN form as an adult literary format. Fate is the thesis, Unlimited Blade Works is the antithesis, Heaven's Feel is the synthesis, and the game genuinely demands you read them in that order — it gates UBW and HF until the previous route closes.

Each route rewrites the meaning of the same early-game scenes. Shirou's first meeting with Saber reads differently after UBW than it did after Fate, and differently again after HF. That re-reading is the mechanic, and no other VN uses it as ambitiously.