From Harper's Magazine 

Nathaniel Hawthorne¡¯s ¡°Celestial Railroad¡± can easily be read in a quick sitting and is a first-class parody. Moreover, Hawthorne is sufficiently clever in going about his task that he lampoons just about everybody and leaves a certain degree of doubt about exactly where he stands. Those who know Hawthorne¡¯s works from high school or college associate him with the stern Puritanism that underlies (and is critiqued in) The Scarlet Letter, but they may also know his flirtations with Transcendentalism and Renaissance humanism apparent in works like The Marble Faun. This story stands astride these two tendencies in his writing. At the first level, he is parodying the classic work of Puritan literature, John Bunyan¡¯s Pilgrim¡¯s Progress. This he does brilliantly. It¡¯s clear that he, like many of the intellectual leaders of New England in the early nineteenth century, finds the Puritan approach to religion a bit tired and ill-attuned to the modern world. They examine a number of alternatives–German idealism, especially Transcendentalism, Catholicism, and even faith in science. The mature Hawthorne exhibits fascination for German philosophy and for the Catholic faith and particularly the culture in Italy that it has helped to shape, but in this short story they receive a back of the hand. The strongest contempt is reserved for blind faith in science. That takes the form of the celestial railroad itself–together with its promise to whisk its passengers to the Celestial City without the trials and ordeals that Bunyan faced on his pilgrimage. This faith is misplaced, Hawthorne tells us–the railroad offers an amusing ride, but it never pulls into the end station. Hawthorne plainly has more sympathy for the stout-hearted faith of Bunyan¡¯s hero. But he also sees that the Puritan model foments intolerance and has a latent hostility to science that holds its people back. These shortcomings must be overcome, just as the essential truth of the pilgrim¡¯s tale is preserved. 

From enote

 

Nathaniel Hawthorne's "The Celestial Railroad" is a parody of John Bunyan's Pilgrim's Progress in which the allegory's main character, Christian, appears in a dream to the author. Like Bunyan's protagonist, Hawthorne's Christian also tries to get ¡°from this world to that which is to come¡± by fleeing the City of Destruction. But, in "The Celestial Railroad" Christian can take a train rather than make the long pilgrimage on foot, so he opts for the "easy way." But, on the trip, the narrator notices that all the landmarks described by Bunyan are somehow altered. For instance, whereas Christian found Vanity Fair sordid, Hawthorne's Christian notices its attractiveness: 

...as the new railroad brings with it great trade and a constant influx of strangers, the lord of Vanity...and the capitalists of the city are among the largest stockholders. Many passengers stop to take their pleasure or make their profit in the Fair, instead of going onward to the Celestial City.

....I can truly say that my abode in the city was mainly agreeable, and my intercourse with the inhabitants productive of much amusement and instruction.

Christian notices that this city now is inhabited with men of the cloth who impart their Christian teachings; such ministers as the Reverend "Mr. Stumble-at-truth," "Mr. This-today" and Mr. "That-tomorrow" contribute. But, Christian speaks to two of the pilgrims on foot who warn him if he remains on the train he will get nowhere because the Lord of the Celestial City has refused to accept "an act of incorporation" for this railroad (which represents blind faith in science), and without that no one can enter the Celestial City.

Clearly, Hawthorne has more sympathy for the stout Puritan pilgrims who are representative of Bunyan's story. However, he also perceives the intolerance of these Puritans and their hostility to science which holds them back from progress. 

Instead of the castle of Despair as in Bunyan's piece, Hawthorne's pilgrim finds it replaced by "Mr. Flimsy-faith," who has repaired the place and offers entertainment. Then, as the train nears its destination, the narrator/pilgrim sees the two pilgrims who warned him at Vanity Fair; they are being accepted into the Celestial City. When the narrator worries about his and the other passengers' reception, Mr. Smoothit-Away tells him "Never fear! Never fear!"

After they board the ferry that they hope will take them to the Celestial City, the narrator asks Mr. Smoothit-Away if he is not coming. With an odd smile, he answers that he is not, but he will see Christian again; as he speaks, smoke is emitted from his mouth and a fire is in his eye. It is then that the narrator realizes that he has been tricked by the devil and the train will never arrive at the Celestial City, but, fortunately he awakens from his dream.

Clearly, Hawthorne admires the stout faith of Bunyan's Christian. However, because Vanity Fair is depicted as having some value, he perceives the Puritan pilgrims as too intolerant against progress and science, as represented by the railroad.