Admittedly, I had never heard of this until I saw a story about the film, on the news. This is probably going to go down as David Mitchell's magnum opus. And rightfully so, it's very creative for a book that has commercial appeal. I don't want to tackle the various motifs and plot, per se. I think that spoilers are immanent if you dissect someone's work like that. But I do want to talk about what I liked and didn't like from a more literary viewpoint.
First off is the complexity. The only reason I'm addressing this first is because it's been touted as a main selling point. To anyone who's taken on authors like Gaddis, Joyce, Wallace, Pynchon, etc, the plot will read fairly streamlined in comparison. However, I don't think it was ever Mitchell's intention to be too mysterious, ambiguous, and base his plot on underlining, complex mathematical themes. It's definitely accessible to anyone. Also, I think the complexity hype has more to do with the average reader experiencing some substance for the first time in their lives. And in that regard, it has more creativity and meaning than 99 percent of what you'd typically find on the New York Times' best seller list.