Book recommendations for japanese history, etc....

It depends really. If that's something you're particularly interested in, then that's a good book to start out with, Obviously, its an Osprey title, so its easy to read with little jargon. If that really piques your interest in the topic, you can move on to Conlan's In Little Need of Divine Intervention, which covers the topic more thoroughly.

Thennnnnnn if Conlan's monograph interests you, you can pick up Court and Bakufu in Japan. Which is a collection of essays edited by Jeffrey Mass. This is a nice handling of Kamakura Japan (Which is the period that contained the Mongol Invasions.)

And thennnn you could look at The Bakufu in Japanese History, which is a collection of essays that deals with all 3 of Japan's Shogunates. This will give you a good feel for the Kamakura, Muromachi and Tokugawa Bakufu, respectively.

After that, the possibilities are endless....