Whose books are these?针对的是These are my books.提问
而Whose are these books?针对的是These books are mine.提问
前者是my定语,后者mine是表语。
还有你后面想表达的意思我理解。
不过你应该讨论的是who does this book belong to?还是whom does this book belong to?
两者理论上都行,whom是who的宾格形式,但在非正式文体中,一般用who。在口语中,一般不用whom,特别是在疑问句中。在正式文体中,whom置于介词后非常正式,如:To whom does this book belong?
追问你是老师吗
追答我已工作