I read this book about 1-Jul-2014. I've read this book before. The book is copyright 1941. This note was last modified Thursday, 24-Jul-2014 21:44:52 PDT.
This note contains spoilers for the book.
This one was done by Heinlein from a description of the story that John W. Campbell gave him. The first installment of this was published in Astounding in January 1941, so it's well before the US was in World War II, and should have been before the population had been whipped into a froth of anti-Japanese prejudice. However, the book version appeared in 1949, and I don't know if (or how much) they differ.
People complain about this book being racist. I read it as Heinlein working to be anti-racist in 1941 terms. I'm not sure what things in this book simply shouldn't ever be done in a book. Mostly people making that complaint aren't very specific (I think they're working from old memories); that does make it hard to refute.
Certainly there are things in this book to complain about!
First, a considerable amount of the science turns out not to work, either definitely, or probably (after all, he doesn't give a lot of details). 1941 was pretty early in our understanding of genetics.
Since the rays that disrupt the cells being tunable by race depends on details of the ray physics that aren't specified, this can't be said to be wrong absolutely. However, we now know just how little genetic difference there is between the so-called "races" (a term with no biological meaning, remember), and it seems very unlikely that the ray could be tuned precisely enough to distinguish effectively (for that matter, it probably couldn't act on humans but not chimpanzees, the DNA is so similar). I think the book kind of hints that it's differences in haemoglobin that are actually exploited by the ray, and I think that has turned out to not be valid either (so far as I know it's the same in all of us). If so, that also doesn't explain how bacteria are killed.
The ability to kill off all infective bacteria using the ray for all frequencies except the right race of human would, in fact, horribly disrupt our bodies. The amount of human life that's really bacteria living in us has been quite surprising; killing all of them wouldn't make us instantly healthy! Also, it's not clear to me that the ray could also disrupt viruses.
The basic setting of this book is in a United States that has lost a war to the Pan Asians, an empire that appears to include China, Japan, Korea, probably Thailand and Cambodia and Laos and Vietnam, and apparently at least part of Russia as well. Cities have been nuked, and the United States is now occupied by their troops. There's essentially no information given on how long it took to form this empire, or how it was done, so it's hard to say if what's shown of their culture makes any sense. Since it's a minor side-issue to this book, it's very sketchily described.
The only races mentioned are Americans, and Pan Asians. He talks about tuning the ray to kill everybody except white people, without worrying about the possibility that there might be African people, or for that matter Native Americans, around (not thinking of their existence and not caring; they're never mentioned at all). He does actually deal with the fact that some Americans have Asian ancestry -- he has the one Asian man in the patriot group (who has had to face a lot of prejudice, and been badly treated by both sides) die heroically.
With what we know about genetic diversity today, the simple lines drawn in the book don't make any sense. And the book clearly takes the non-scientific concept "race" seriously, and treats it as scientifically meaningful. I think perhaps this book is too deeply mired in the racial ideas of the past to be worth reading for anything except historical interest.
One thing this book does that's amusing and not like other Heinlein—the clever guy who figures out how to make things work is a PR expert, not an engineer. Since a lot of what they do is essentially psychological warfare work it kind of makes sense for him to be.