I read this book a couple months ago. I liked it, but I think that saying most details are factually correct is a stretch. Certainly the major, historically verifiable facts probably are, but by volume it's got to be mostly made up: it's a book set in the mind of someone Herzog probably interviewed briefly, likely through a translator. There's just no way I believe the running narration is based mostly on details Onoda provided, there's just too many of them and they're too specific. Don't get me wrong, it's a neat book, and Herzog has earned so much respect from me that he can claim whatever he wants.