Narrators hold different positions in the stories they tell. First person narrators tell the story from an interactive position. He/she is one of the characters, and readers generally cannot know anything the narrator doesn't know. Both Fitzgerald's narrator Nick in The Great Gatsby and Vonnegut's narrator in Cat's Cradle are first person narrators, and while they share some similarities, they are also very different.

Vonnegut's narrator John is a first-person central narrator, meaning that he is not just the narrator, he is also the main character. Everything John sees, readers see. Everywhere John goes, readers go. Everything John thinks, readers can 'hear.' Readers also receive all the story's details from John. There are no other characters who really contribute to our understanding of the story. Even when we 'hear' other characters speaking or reacting, it is really John relating what he hears and what he thinks other characters think.

Fitzgerald's narrator Nick is, similarly, a first-person narrator, but he is really more of a peripheral narrator. Rather than being the main character, Nick is only one character of many, but in his position as a peripheral narrator, Nick’s job is to hear and convey to the reader everyone else's stories.

One question that a reader must ask of a narrator is whether or not he/she is reliable or unreliable. A reliable narrator is one who is consistent in his/her story and in the world he/she creates for the reader. He/she tells the truth and (usually) nothing but. An unreliable narrator is one whose story cannot be taken at face value. He/she has little or no credibility. This can be for a number of reasons, including insanity, lying, or just a total lack of moral character. Both John and Nick are similar yet again in that they are unreliable narrators, but they differ in the reason why. 

John is an unreliable narrator because he is a liar. Some would argue that John is a reliable narrator because although he lies, he is honest about the fact that he is lying. We can see this immediately in the novel's epigraph:

"Nothing in this book is true.
Live by the foma that make you brave and kind and healthy and happy.
The Book of Bokonon 1:5" (Vonnegut, 1963, p.1)

However, honesty about lying still does not reveal truth to the reader, so even here in the epigraph, where 'foma' translates as 'lies,' we see that John is unreliable. We can see other evidence in the text as well. In Chapter 3, John writes, "In the autobiographical section of The Books of Bokanon he writes a parable on the folly of pretending to discover, to understand" (p. 6), which seems to suggest that the search for truth displays a lack of good sense and that perhaps truth is relative. In Chapter 15, John shares Dr. Breed's opinion that "everybody does about the same amount of thinking. Scientists simply think about things in one way, and other people think about things in others" (p. 22). Again, this suggests that truth is relative. Although everyone thinks, they all think in different ways and emphasize different things. In another example, John is discussing Dr. Hoenikker's death with Miss Faust:

"Dr. Breed keeps telling me the main thing with Dr. Hoenikker was truth."

"You don't seem to agree."

"I don't know whether I agree or not. I just have trouble understanding how truth, all by itself, could be enough for a person." (pp. 33-34)

Here, John clearly indicates that he believes truth is not enough to make living and the knowledge of impending death bearable. He seems to believe that there needs to be something other than truth to ameliorate the burdens of living life. His own lies paired with his consistent questioning of an objective Truth makes John a classic unreliable narrator.

Nick is also an unreliable narrator, but it's not necessarily because he's a liar. Rather, it's because he sees himself as morally superior to those whose stories he tells. The novel begins with this revelation:

‘Whenever you feel like criticizing any one,’ [my father] told me, ‘just remember that all the people in this world haven’t had the advantages that you’ve had.’ He didn’t say any more but we’ve always been unusually communicative in a reserved way, and I understood that he meant a great deal more than that. In consequence I’m inclined to reserve all judgment. (Fitzgerald, 1925. p. 3)

Any time a narrator proclaims himself to be morally superior in any way, the reader should pay particular and close attention to how that narrator functions in the story. And in this story, Nick, despite his assertion to the contrary, does a lot of judging. He begins by telling us that Gatsby "represented everything for which [he has] an unaffected scorn" (p. 4). In his outing with Tom and Daisy, Nick sees Myrtle, whom he describes as having a "simple mind" (p. 133), but he doesn't have anything particularly nice to say about Tom and Daisy, either: 

They were careless people, Tom and Daisy—they smashed up things and creatures and then retreated back into their money or their vast carelessness or whatever it was that kept them together, and let other people clean up the mess they had made…. (p. 191).

But Nick's reliability as a narrator doesn't just hinge on the lack of continuity between his perception of himself as a non-judgmental person and the reality that he is. He also undermines his credibility by engaging in many of the same activities and behaviors for which he judges everyone else. For example, although Nick has a girlfriend back home, he flirts with Jordan and has a casual fling with a girl in the city. He comments on the drunken guests at Myrtle's party, but he gets just as drunk as the rest of them. And at the end, Jordan calls him out:

'You said a bad driver was only safe until she met another bad driver? Well, I met another bad driver, didn't I? I mean it was careless of me to make such a wrong guess. I thought you were rather an honest, straightforward person. I thought it was your secret pride' (pp. 189-190).

Nick responds, “I’m thirty. [. . .] I’m five years too old to lie to myself and call it honor” (p. 190). There are some who argue that this change of heart, and Nick's compassionate attention to Gatsby's funeral and ultimate return to the Midwest, allow him to be a reliable narrator, but at this point, the damage is done. First, we have no real idea, because he probably doesn't either, about what Nick is lying. Second, our perspectives and perceptions of the other characters have been well- and permanently shaped. No, Nick is not a reliable narrator.

As to whether or not our narrators' goals have been reached by the end of these novels, it's hard to say. Fitzgerald's Nick wants to leave the monotony of Midwestern life to make his fortune, and he attaches himself to people who live exciting, glamorous lives in the rich fast lane. But in the end (or perhaps from the start), he has little tolerance for the shallow and self-serving people he finds, and he returns to the Midwest, perhaps changed somewhat in character but not in circumstance. Vonnegut's John has perhaps convinced his readers to explore multiple philosophical truths rather than an objective Truth, but only the reader(s) can say whether or not either was successful.

How does John's narration in Cat's Cradle differ from and resemble Nick's in The Great Gatsby?

John and Nick have a lot of similarities. They are both narrators and major characters in their respective stories, for one. Interestingly, though, they are also both a bit on the periphery of the action. Nick is an outsider from the other characters, as he continues to live a moderate life (financially, anyway) and claims to hold Midwestern values while the Eastern characters live lavish, careless existences. Characters are always introducing Nick to people and confiding in him, but Nick himself doesn't do a whole lot to drive the plot and action. Similarly, John comes across as the only sane character in Cat's Cradle, often standing off to the side to allow the eccentricities of the others to shine. Consider Chapter 43, where, after a bit of background information, John simply asks a question and allows Crosby go on and on about his philosophy, putting his "barn-yard clownishness" on full display.

Additionally, both narrators act as a reader surrogates, introducing us to the world and characters of the novel. As a newcomer to the East, Nick is introduced to new people and sees the world of The Great Gatsby through fresh eyes, just as the readers do. His outsider status further allows the readers to identify with him (as most of us aren't lavish millionaires either). Similarly, John in Cat's Cradle acts as an "everyman" type character; there's a reason he has the generic name of "John." The idea behind an "everyman" character is that the reader can put himself or herself in the character's place.

However, these narrators have a few important differences. One of the biggest is their levels of reliability and relationships with "the truth." At the beginning of The Great Gatsby, Nick talks in the very first chapter of his objective honesty and nonjudgmental attitude. He sets himself up as a narrator who will give an unflinchingly honest (but still fair and nonjudgmental) look at the glitzy world of the East. Now, this is certainly a point of contention. As Jordan Baker points out to him, he gets sucked into the life he is "observing" and may be blinded by the glamour. Still, his stated goal as narrator is an honest truth.

This couldn't be further from Cat's Cradle, which begins with the epigraph "Nothing in this book is true." Sure, the quote is from The Book of Bokonon, but it's there for a reason. John is completely upfront about the fact that this story is a lie. He is the definition of an unreliable narrator in that sense. However, he has a very different goal than Nick. Instead of getting a "just the facts" version of the story, John is trying to reach a different, more elusive philosophical truth through the lies. If you've ever read The Things They Carried, there is a similar thing going on here. In some ways, this makes John more reliable than Nick, since John can always be trusted to lie. In short, the narrators' ideas on truth and their reliability are fascinating ways that they differ.