如果是后面的,应该是This is the book...麻烦具体说一下Thisis the book (that) you want to read.book 是先行词，you want to read是定语从句，修饰the bookThis book is the one you want to read.the one是先行词，you want to read是定语从句，修饰 the one再麻烦一下Thisis the book (that) you want to read. 中为什么没有one?因为有先行词了，就不要the one