"Do they sell books?"
Translation:Loro vendono libri?
If I understood all the comments prior to now ... well, here's what I understand:
you can use that sentence formation if you are trying to point out that the books are actually being sold as opposed to being 'read' or 'used' or some other verb ... i.e. the emphasis of the meaning of the sentence is now on the verb. Also my understanding is that the correct formation in Italian is 'subject verb object ?', or SVO? for short. In other words, it might seem backwards to native English speakers, but the 'pieces' of the question are the same order as if you were saying a statement ... differentiated from the statement of course with a question mark at the end :-)