"Usted termina de leer este libro."
Translation:You finish reading this book.
When and/or Why do i use DE LEER vs. just LEER? I often see DE used without apparent rhyme or reason. Why? Gracias
The usual answer to the question why is... because it's Spanish.
The de is associated with terminar, so terminar de means stop or finish.
I've said it before, and I'll say it again now. Use a dictionary to see the meanings and frequent compound forms. http://www.wordreference.com/es/en/translation.asp?spen=terminar
It accepts ud, so it probably takes uds too. I'm not sure about sr and sra, those don't show up much.