Narrative irony techniques include verbal, situational and dramatic irony. They are used by writers to diconnect the events that characters are living from what the reader knows, by the means of presenting a discrepancy between the fact what it has been said about it, which generaly means the opposite situation, as it is shown by Walls in this paragraph from "The Glass Castle":
"Mom explained that since only she and Dad could fit  in the front of the U-Haul, Lori, Brian, Maureen, and I were in for a treat: We got to ride in the back. It  would be fun, she said, a real adventure, but there wouldn’t be any light, so we would have to use all our  resources to entertain one another."
Explanation:
The circumstances for the family´s trip are indeed adverse, but the mother states it would be an fun adventure though, as if traveling in the back, silent, stacked and lightless, would be funny.
The irony occurs in the opposite of the actual meaning.
Mom and Dad rented a great big U-Haul truck" Plus we were not allowed to talk. Since it was illegal to ride in the  back, anyone who heard us might call the cops. Mom told us the trip would be about fourteen hours if we  took the highway, but we should tack on another couple of hours because we might make some scenic  detours.
This inconsistency, the narrative irony technique, between what´s expected and facts happen in three ways:
Verbal irony (not in this case)
Dramatic irony, that manages two levels of  awareness: the character unawareness of the fundamental information, and the fundamental information that has already been revealed to the reader, (not in this case).
Situational irony, the situation features a discrepancy between what is expected and what is a fact, which is out case in this example paragraph.
