When people hear the name Mark Twain, they likely think about The Adventures of Tom Sawyer or its sequel, Adventures of Huckleberry Finn. But Twain had written a lot before either of those works came out.
For many years he had been a newspaper correspondent and commentator, often writing humorous pieces, or “slice of life” stories with a humorous twist (think of someone like Dave Barry). In 1867, Twain set off on a pleasure cruise to Europe and the Holy Land aboard the Quaker City with the intentions of sending back dispatches about his travel to the Daily Alta California of San Francisco; he also sent dispatches to the New York Tribune and the New York Herald.
You can see the itinerary  with dispatches sent to the newspapers, or check out a copy of the travel prospectus  and passenger list . Upon his return to the United States, he commenced on a lecture tour about the trip called “The American Vandal Abroad ” (note: there is no definitive version of any of Twain’s speeches – he would often improvise before an audience, and a speech delivered before one audience might vary greatly from a speech delivered elsewhere).
In 1869, Innocents Abroad: or the New Pilgrims’ Progress , was published to great critical and popular acclaim. The book was Twain’s most popular work during his lifetime.
The book is ostensibly a travelogue, a genre that remains popular (cf. Michael Palin’s books of recent years, such as Sahara ) and which goes back at least as far as the 2nd c. CE (Pausanias’ Guide to Greece  which has served as an indispensable help in reconstructing ancient buildings now lost). Of course, Twain’s travelogue is only part travelogue. A lot of it allows Twain to make humorous and sometimes biting observations of his fellow passengers, and on the locals they meet along the way.
Twain was a master of irony. In this book, this often takes the form of gently ironic observations of people and their idiosyncrasies, as when he observes on the boat over that everyone starts out their voyage eager to keep a travel journal (just as he is doing with his dispatches), but soon, the initial enthusiasm wears off, and such noble intentions fall by the wayside. And he himself makes quick work of the voyage home, stating that his own diary entries for the journey home were sparse and perfunctory.
Twain is quick to point out the differences between our expectations and realities – he notes that the pilgrims all have come to expect a land of wild romance in the Middle East, full of menacing Bedouins, who have to be kept at bay by sharpshooting, eagle-eyed tourists. They got these notions from reading travel guides high on romantic exaggeration and low in relation to reality.
As it turned out, the locals were people simply trying to make a living from the tourists, and the weapons the locals carried in the Middle East were so old and rusty they posed no risk to the travelers. Twain suggests he had more to fear from his gun-totin’ fellow travelers than from the supposedly dangerous locals.
Twain also has an eye for the unusual as evidenced by his chapter on the visit to a Capuchin convent in which the former monks skeletal remains are left about and arranged in neat piles or into artistic representations. The abbot who gives Twain and company the tour seems to know each and every bone lying around – this here is Brother Anselmo, and that’s Brother Thomas and so on.
Twain has a gruesome fascination with this whole scene and goes into a vivid two-page description of the crypt, described as something one might have seen in the Renaissance, had Michelangelo and others used skeletons as their preferred medium.
Twain gets an ironic jab at his guide when he notes that the abbot himself speaks wistfully of his brothers’ remains, adding “I thought he even looked as if he were thinking, with complacent vanity, that his own skull would look well on top of the heap and his own ribs add a charm to the frescoes which possibly they lacked at present.”
As they travel through Europe and on to the Holy Land, Twain also reflects a bitter disappointment between the ideals of Christianity and its practice. As someone raised in the Protestant tradition, and not a very fervent Christian himself, he views Catholicism with a bemused and somewhat critical eye, but more than once he notes the discrepancy between the professed Chrisitianity of some of his fellow pilgrims and their intolerance of others who differ from them in belief. On the other hand, he is very impressed with some of the monasteries in the desert of the Holy Land. The monks there welcome rich and poor alike and all are treated to radical hospitality which impresses Twain as fitting the spirit of Christianity.
The work has an added fascination in depicting the Americo-centric view of Twain and his travelers. In their travels, Twain and his company refer to all tour guides as “Ferguson” as that is easy to remember and pronounce than the guides’ real names (which Twain never tells us). And while Twain is very sensitive to and observant of the discrepancy between reality and our perceptions thereof, he never fully escapes the prejudices of his own age – unless, here too, he is pulling our leg.