You__C_read this book if you don't want to.=== You don't have / need to read this book if you don't want to. 因为这里强调的是必要性,所以用needn't 强调许可性,我们用mustn't. 强调能力,我们用can't 再问: 这个不是主将从现吗? 再答: 你好。请记住,一切情态动词本身已经包含了“现在或将来”的概念, I needn't go now . I needn't go tomorrow. 明白了吗?