"Do they know the book?"
Translation:Kennen sie das Buch?
When I make sense of the German sentence structure for myself a more reasonable direct translation would be..
"Know them (about/of) the book?" rather than "they".
This seems to be the easiest way I can see to understand and remember the way the sentences in German are formed.
Another example might be..
"Magst du das buch?" as "Like you the book?".
In any case here putting the verb (know/like) before the pronoun (them/you) changes the sentence into a question without the need for another word ("Do").
Those clever Germans >:)
Nein, das kann man nicht sagen. You can't say that in German. Das macht keinen Sinn. It makes no sense.
And in this sentence the 'sie' means 'they', not 'you' (The polite 'you' is 'Sie' with capital 'S').
You could say:
'Wissen sie (irgend)etwas über das Buch?' 'Do they know anything about the book?'
'Wissen sie von dem Buch?' 'Do they know about the book?'