Domain - James Herbert (Book 3 in the Rats Trilogy)

The long-dreaded nuclear conflict.

The city torn apart, shattered, its people destroyed or mutilated beyond hope. For just a few, survival is possible only beneath the wrecked streets – if there is time to avoid the slow-descending poisonous ashes. But below, the rats, demonic offspring of their irradiated forebears, are waiting.

They know that Man is weakened, become frail. Has become their prey