I didn't know that Libros, Libros was closed. When I traveled to Mexico in November, I didn't look for a book store in Cabo San Lucas like I normally do, because this time, I brought my Kindle. I think I remember seeing a bookstore at Puerto Paraiso which is the 3-story mall right on the marina.
I also did some research online for you and someone mentioned that there is a book store in the Plaza de la Danza which is near the Boulevard Marina.