The ending of Pedro Páramo the book is, appropriately, the end of Pedro Páramo the man. He has just been stabbed by drunk Abundio, and is staggering into the house at Media Luna. The very last line states that, "He fell to the ground with a thud, and lay there, collapsed like a pile of rocks" (68.14).
Remember when we said that "Pedro" means stone? Well, here the simile is pretty neat: Pedro, the stone, falls to the ground and lays there like a pile of rocks. It's like he's finally fulfilled his name and become, like a stone, a dead and infertile part of the earth.
The fact that the book ends abruptly too, almost with a rock-like thud, emphasizes the fact that Pedro makes the book—without him, there would be no visit to Comala, and no story.