"Sir, do you have two books?"
Translation:Señor, ¿tiene usted dos libros?
"Tenga" is the command form and the subjunctive form, neither of which is needed for this question.
¿Tiene (usted) dos libros? Do you have two books?
¡Tenga (usted) dos libros! Here are (Have) two books!
Quiero que (usted) tenga dos libros. I want you to have two books.