The Innocents Abroad, or The New Pilgrims' Progress was published by American author Mark Twain in 1869. The travel literature chronicles Twain's pleasure cruise on board the chartered vessel Quaker City (formerly USS Quaker City) through Europe and the Holy Land with a group of religious pilgrims in 1867. It was the best selling of Twain's works during his lifetime. At first blush, Innocents Abroad is an ordinary travel book. It is based on an actual expedition, in a retired Civil War ship (the USS Quaker City). The excursion upon which the book is based was billed as a Holy Land expedition, with numerous stops along the coast of the Mediterranean Sea, as well as a train excursion from Marseilles, France to Paris for the 1867 Paris Expedition, and a side trip through the Black Sea to Odessa, all before the ultimate pilgrimage to the Holy Land. Twain records his observations and critiques of various aspects of culture and society he meets while on his journey, some more serious than others, which gradually turn from witty and comedic to biting and bitter as he progresses closer to the Holy Land. Interestingly, once in the Holy Land proper, his tone shifts again, this time to a combination of his former light-hearted comedy and a reverence not unlike the attitude he had previously mocked in his traveling companions.