One of my top five books. I've read it so many times that the binding broke and the book is now in three pieces. I'm amazed that James Clavell managed to capture the culture so well.
I've read only Noble House. It's quite rich on the culture--maybe not so much as Shogun--and captures the setting quite well, but I didn't find it nearly as entrancing as Shogun.
Clavell's whole Asian Saga (Shogun, Tai-Pan, Gai-Jin, King Rat, Noble House, and Whirlwind) is amazing. My favorite is Tai-Pan - the book had a tremendous impact on me, and I'd imagine it would appeal to every real entrepreneur. The underlying themes are freedom, individualism, honor, risk-taking, and ultimately, building something and defending it.