Shogun has a good reputation as a must read historical novel. It depicts Japan in the beginning of the 17th century when English and Dutch manned ships reached its coastline for the first time (after Portuguese).
I really like reading historical novels but there should be some limit for its size. This particular novel has around 800-1100 pages (depending on book style).
This is a fiction, so I don't understand why would the author decide to provide such detailed accounts of everyday life in Japan or conversations between different people. Many of them are unnecessary and repetitive.
I would admit that after reading for about 300 pages, I became utterly bored by its narrative.
Some of the ideas in the book made no sense. For example, the author imagines that for even slightest deviation from the order or culture norms of the 17th century Japan, samurais were willing to commit ritual suicide. If indeed that was case there would be no samurai left alive to participate in the actual wars.
Moreover, the author depicts future Shogun escaping from the enemy's castle dressed as a woman. Such "escape" would have considered quite dishonorable act by any samurai standards, especially by a person who was aiming to be the first man in Japan.
Reference to vegetarianism among samurai class in 17th century Japan is also questionable, especially when they were freely eating fish products. More accuracy would have been beneficial for such a monumental work.