The Innocents Abroad is a travel book by American author Mark Twain which humorously chronicles what Twain called his "Great Pleasure Excursion" on board the chartered vessel Quaker City through Europe and the Holy Land with a group of American travelers. It was the best selling of Twain's works during his lifetime and one of the best selling travel books of all time. 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, and a side trip through the Black Sea to Odessa, all before the ultimate pilgrimage to the Holy Land. Twain recorded his observations and critiques of various aspects of culture and society he met on the journey, some more serious than others, which gradually turned from witty and comedic to biting and bitter as he drew closer to the Holy Land. Once in the Holy Land proper, his tone shifted again, this time to a combination of light-hearted comedy and a reverence not unlike what he had previously mocked in his traveling companions.