I finished Cloud Atlas by David Mitchell. That was a complex book. I went to the Wikipedia entry for the novel when I was done, because the central story (of the 6 interlocking narratives) didn't make much sense to me. Wikipedia cleared it up nicely. Also, the author explained (in the Wikipedia entry) how there are "transmigrating souls" in the story, pointing out that each of the 6 main characters has a birthmark. I noticed they all had a birthmark, but I didn't jump from there to transmigrating souls. The New York Times compared the book to a challenging crossword puzzle.