What writing technique is used by Mark Twain in The Adventures of Tom Sawyer?

The Adventures of Tom
Sawyer is written in an episodic, humorous
way.

More than a single storyline, the book
is written in an episodic way with multiple separate storylines.  Once the story begins
moving along to the climactic incidents of the cave and the treasure, we start to have a
longer plot line.  However the beginning of the book is made up of several brief plot
lines lasting a chapter or two.

By using episodes, Twain
keeps the story light and humorous.  It is not until the end that things really seem
serious, but even serious events like the murderous Injun Joe are treated with humor. 
When Tom fakes his death, there is a pang of sorrow, but the story is still funnier than
it is sad.