These sentences are in the indicative mood, which means the direct object pronoun will come directly before the verb in the sentence.
The direct object pronoun for the object los libros in the first sentence is los. Remember, the direct object pronoun comes before the verb, so the sentence becomes:
No los leas. "You don't read them."
The direct object pronoun for the singular object el libro in the second sentence is lo. Following the same rule as above, the sentence becomes:
La camarera te servirá el plato de pasta con mariscos. Isabel nos lleva la sal y la pimienta a la mesa. Javier me pidió el aceite y el vinagre anoche. El dueño nos busca una mesa para seis personas. Tu madre me consigue unas uvas deliciosas. Te recomiendo este restaurante Lola y Paco
JAN. 27, 2015 Spanish Defense Ministry confirms that Greek F-16 fighter jet killed at least 10 people after it crashed into other planes on ground during NATO training program.