Biodroid, I've chimed in on James Clavell a number of times in the GRRM forum. I read Shogun when I was fifteen or sixteen... and I thought it was great. I loved the overall scope and the layers upon layers of political intrigue.
Clavell takes a number of liberties with the actual characters, timelines, technology, and religion, but these changes (I feel they're minor in comparison to the size of the story) really help define the setting. For instance, 1. Guns were used before the decisive battle of Sekigahara, 2. There is no evidence that Will Adams (Blackthorne) had any romantic feelings for Gracia Hosokawa (Mariko), 3. The term Geisha originated at least 150 years after the events of Shogun, 4. De Liefde (Erasmus) made landfall on Kyushu and not Hokkaido. Anyway, the story inspired me to read up on the transition from the Sengoku period to the Tokugawa Shogunate... so I thought that Clavell's liberties enhanced the story for an American teenager.
For over twenty years, I've looked for epic political struggles like Shogun. Dune, Frederick Forsyth's stories, Tom Clancy's stories, Malazan Book of the Fallen, The Illiad, The Riftwar Saga, Dan Simmons' stories, and HBO's ROME all had aspects of intrigue, schemes, and betrayal in political settings. Some suceeded better than others, but none quite had the exquisite and engrossing touch that Shogun had.... That is until I picked up GRRM's A Song of Ice and Fire epic. Happy reading.