You may try to find out which the book you want (be)want 后面应该填什么,为什么这样填?
问题描述：
You may try to find out which the book you want (be)
want 后面应该填什么,为什么这样填?
答
应该填 is
which the book you want is是一个宾语从句
如果把它变成单独的一个句子就是:
Which is the book you want?
所以原句只不过是把这个句子变成了陈述句语序,所以把is 放到了后面