James Clavell's Shogun: The contrast between the Japanese and European cultures in 1600 are delicious, the characters and plot both well developed. I've read it at least a dozen times over four decades. As I age, I find I experience it very differently.
Shogun's a milestone in my reading history - it's so extraordinarily engrossing. It deflated me more than any other book as I turned each of the final, waning pages because I didn't want to leave its world behind.
I was briefly elated to see there are "sequels" but just as quickly disappointed to learn they're set centuries apart; it ended up feeling like I was clinging to the only album ever made by an amazing band. I've yet to read the other books in the saga, but I should circle back and fix that.