"Lost in the Funhouse" is a story by John Barth, and it exhibits many postmodern characteristics. Let's look at some examples to help you get started.
In "Lost in the Funhouse," we find reference to italics in a way that suggests metafiction (a story that is aware of itself as a story). The point of view of this story is that of a narrator, but Ambrose's point of view also plays in. Notice, too, how the story's chronology shifts through the blend of past and present verb tenses and the flashbacks to the time of Ambrose's father.
The narrative is quite fragmented, jumping back and forth as it speaks of going to Ocean City and then takes a break for a reflection of physical descriptions (note the metafiction here, too). Imagery is involved in this descriptive section, as well as a reflection on simile and metaphor.
The narrator essentially gives us his own stream of consciousness throughout this story, breaking the narrative for these meditations. This produces fragmentation.
Intertextuality appears in the reference to a popular song but also in the philosophical ideas woven throughout the story. Look for references to acting and being.
Indeed, the meaning of this story is rather hard to grasp, and we do not know how much of the narrator's descriptions to trust as we try to follow. The lines between fiction and reality blur significantly as the narrator continues to interrupt himself.