Black Swan Green and Ghostwritten, short story collections, though the stories are not disparate but intertwined (e.g., Black Swan Green is all about same boy over the course of a year). Cloud Atlas is somewhat different, being comprised of what almost seems to be six excerpts from other novels. There's (story 1) a man at sea suffering from an odd brain ailment; (story 2) a young composer working with an aged and renowned composer; (story 3) a woman investigating an energy conspiracy; (story 4) an elderly man held against his will at a nursing home; (story 5) a human "fabricant" who discovers she's a slave; and (story 6) a primitive young boy exposed to truths of his world. The novel begins at the chronological beginning with story 1, continues through story 6, then returns chronologically backwards, ending with story 1. In doing so, Mitchell leaves cliffhangers in each story while interweaving each piece together.
I suppose the structure could come off gimmicky, but I quite liked it. I also enjoyed getting snippets of different voices, worlds, and even genres (story 3 is a mystery; story 5 sci-fi). There are some issues--the bad guys seemed too stereotypically bad in story 3, and there's some odd loose ends in story 4--but none of that kept me from enjoying the book.
The stories have some literal connections (like the protagonist of story 4 reads the book of story 3), but the real connections are thematic. In each, the protagonist must become aware of his or her surroundings and stand up for him or herself against greater forces. Not all survive doing so, but Mitchell has given each a sense or glimpse of freedom once that risk is taken.