1. She put the book tight into its slipcase. --> because 'tight' is a final state, this wording emphasises the final state "tight" more than 'put'. 2. She put the book tightly into its slipcase. --> because 'tightly' modifies 'put' the emphasis is on 'put' with a strong emphasis on 'tightly' (which can have more or less emphasis than the put).