What are some examples of irony in The Glass Castle by Jeanette Walls?

Probably the strongest example of irony is one we learn as
the book ends.  Jeannette's mother Rosemary had considerable wealth that could have fed
and clothed her children and provided a home for them, but she felt she needed to hold
on to this property.  This irony is foreshadowed by the children's discovery of a
diamond ring.  When they learn that it is a real diamond, they want to sell it, but
Rosemary says that she "should have nice things." 

The
title The Glass Castle highlights the irony of the castle Jeannette's father Rex
promises the children.  Although he is knowledgeable scientifically, it becomes clear to
us that the glass castle will never truly exist.  It is ironic that he describes it as
glass because glass is fragile and unsustainable, like the Walls family itself.  It is
also ironic in that it suggests a fairy tale existence in contrast to the squalor in
which the family actually lives. 

We can see irony in the
loyalty and love the children have toward their parents despite what many of us would
consider neglect and even abuse.  It is this mix of love and dysfunction that makes this
a conflicted and powerful book.  

There is even irony in
author Jeannette Walls' fear of what people would think of her after she published the
book. In an interview she claims that she was fearful of people's reactions.  This is
ironic in light of the resiliency she shows in the book itself, but it also reflects the
mix of vulnerability and resiliency (possibly an ironic mix) that drives the narrative
of this book.