The choice of the metaphor is deliberate. For while much of Twain's writing was funny, even hilarious, his work also displays a great deal of melancholy and pathos. The darker qualities became more prevalent as the author aged, partly because of personal losses (the deaths of two of his daughters and his wife) and partly because he developed a bleaker view of the human condition.
This Library of America edition, though, presents a younger, happier Twain. The Innocents Abroad; Roughing It constitutes two of the author's best "travelogues" -- extended essays, really, chronicling the author's wanderings.
The Innocents Abroad focuses on Europe and "the Holy Land," as Twain referred to it -- but readers will find little reverence here for tradition and custom. Twain in these pages ridicules pomposity wherever he finds it.
Roughing It is even funnier, being a record of Twain's journey through the American West to Hawaii. Roughing It presents a whole cast of memorable and humorous characters, from miners to ministers to newspaper editors who dueled with pistols.
Ostensibly nonfiction, both these books feature "tall tales"; in them, the author exaggerates for effect, both to achieve greater drama and make the reader laugh all the harder. My favorite passage in the Twain canon is incorporated into Roughing It; it's called "His Grandfather's Old Ram," and features a gloriously inebriated miner trying to tell a story but failing to stay on point. His drunken meanderings down his personal memory lane never fail to make me chortle.