Toward the beginning of this book, it looks as though the narrator might be a limited omniscient because it only reports the thoughts and actions of our main character, the kid. But the book opens into other characters' minds as it moves into its second half. When Glanton looks into a fire, for example, we read:
That night Glanton stared long into the embers of the fire. All about him his men were sleeping but much was changed. So many gone, defected or dead. The Delawares all slain. (17.9)
These lines clearly show what Glanton is thinking, which means the omniscient narrator has expanded our access beyond the mind of just the kid and into the minds of other characters. That said, the narrator is also very reluctant to make these openings, just like the roughneck characters are reluctant to show their inner feelings to anyone.