Kuribayashi is described in rather positive terms. Unlike standard Japanese commanders of the time, he is said to have been not just empathic commander who cared deeply about his subordinates, but also unwilling to waste their lives in useless Banzai charges. Instead, he concentrated his effort on building up not only a massive defense system of tunnels and protected positions in depth to slow the American attack down, but also on building up the competence and confidence of his men, until he had a strong, tightly-knit fighting force that fought on despite the horrible conditions of the battle and a tremendous disparity in resources. This was done under some opposition from his subordinate commanders at the island, as it wasn't in accordance with Japanese doctrine, which concentrated on trying to stop the invasion at the beach. Kuribayashi realized, however, that with the tremendous amount of firepower the Americans would be able to direct at such positions, they'd be overwhelmed in very short order.
And I have to admit, not only is it interesting to see how Kuribayashi went about shaping the defense of the island, it is also worthwhile to read his biography-within-the-book and see not mainly what shaped the man, but perhaps more what sort of world it was that he encountered during his career not just in Japan, but also overseas in the U.S. (as deputy military attaché) and Canada (as military attaché).
There are also chapters on the political history behind Japan's opening to the West in the 1800s (forced to do so by American warships), the Meiji Restoration, and the drift from liberalization and democratization in the early 1900s towards militarization and war, with military interventions in Siberia, Manchuria, Korea and China and Indochina, and on the consequences of the war for the defeated Japan. And it's there somewhere that Duke loses me a little, but more on that in a minute.
As I said, the book is, at least initially, built around the letters the Lieutenant General wrote to his family, mainly his wife, from Iwo Jima. Those letters are interesting in themselves; the General discusses his own probable death there, the unbearable conditions with hordes of vicious insects and American bombers harassing them at night, making it impossible to get a full night's sleep, and the heat – not just from the sun, but from the volcanic island itself, making in some spots impossible for the men to keep digging in the same place for a longer period of time, because it melts their rubber sandals – but she shouldn't worry, because he's fine. He also issues exhortations to his son to get a grip and make something of himself, to his little daughter to make sure she wears enough clothes so that she doesn't catch a cold, and to his wife to stop sending him food and to for God's sake get the hell out of Tokyo with the family while she can, because once Iwo Jima falls, the Americans are going to make an airfield out of it and bomb Tokyo into a burnt-out ruin.
The "for God's sake get the hell" part isn't actually in the very polite letters, but I do get a clear impression that's what he's actually thinking. (At least it is what I'm thinking, since he tells her that from the start and she never seems to get it.) The book doesn't go into detail on what the General did while stationed on the Asian mainland, unfortunately.
But back to where Duke loses me a bit: her depiction of how Japan was provoked and more or less, it seems, forced into war. She tells her readers about how Japan felt insulted when the Western powers wouldn't let it make territorial gains from WWI, how it felt they conspired to keep it from taking its rightful place in the sun, how they prevented her from territorial gains in China while taking their own chunks of land quite happily, etc. In other words, Japan felt the Western imperialist powers were hypocrites for not letting it do what they had already done.
Duke also blames Chiang Kai-Shek for escalating the Marco Polo Bridge incident into the Second Sino-Japanese War by holding a provocative speech, which seems to go very lightly on the responsibility of the Japanese government. Overall, she seems to go one step too far in her attempts to mitigate the responsibility of Japan for the outbreak of war in the Pacific. Even if the US and England may well have given Japan far less space for imperial expansion than Japan might have wanted, I can't see that as an in any way sufficient reason for annexing Korea, invading Manchuria, and generally making a bloody nuisance of itself. Europe is responsible for its own imperialistic behavior towards Asia, Africa, and... well, everybody, and I think a similar attitude must be taken towards Japanese imperialistic ambitions. The intense suffering of the Japanese people during and immediately after WWII does not justify taking responsibility away from the Japanese leaders for their decisions.
Duke's criticism of U.S. policies also falls into similar territory for me; the discrimination and prejudice against Japanese-Americans is highly deserving of criticism, but t doesn't in any way justify militaristic, expansionistic Japanese policies. (And, while I'm on this subject: as long as Japanese soldiers keep fighting and killing American soldiers, there is no reason for those American soldiers to not keep trying to find and capture or kill those Japanese soldiers. Duke calls that "a systematic hunt for the survivors", but it's not. It's called "war", where as long as somebody is trying to kill you, you're perfectly within your rights to try to stop him from killing you, including by killing him as well.)
Apart from that aspect – which doesn't dominate the book – I think this is a worthwhile read; Duke writes a very readable prose. And when you've finished the book, you can see the Clint Eastwood movie, which is excellent.
(Here is a review by an actual historian and not a mere dilettante such as myself.)