And if it were anybody but Heinlein, I'd say the hell with it.
All right, look -- between 1959 and 1964 Heinlein wrote what I regard as his three _preachiest_ books: _Starship Troopers_, _Farnham's Freehold_, and this one. _Troopers_ and _Farnham_, whatever their flaws (and I think _Farnham_ is a much, much worse book than _Troopers_), were about subjects in which Heinlein had some expertise -- respectively, military service and surviving a nuclear attack. But Heinlein was never a _parent_ anywhere but in his dreams.
And yet -- in this sorta-juvenile novel ostensibly about young Podkayne Fries of Mars but actually, albeit indirectly, about her younger brother Clark -- there he is up on his soapbox, blaming Mom for not staying home with the kids. _That_, y'see, is why the terrible thing happens to Poddy at the end, and why Clarkie is turning out to be such a sociopath: their mother was just too busy with her _career_. (As an engineer.)
_Which_ terrible thing happens to Poddy depends on which ending you read. As Heinlein originally wrote it, she died; as he _re_wrote it (at Putnam's behest), she was merely comatose, with every hope of recovery. In the most recent PB edition of the novel, both ending are included, along with a bunch of comments/votes from readers who had much stronger feelings about the matter than I do.
Call me an ol' sourpuss, but I don't even especially _like_ Poddy. She's sorta cute in a late-50s kiddie-lit way, but the folks who say this book is dated are entirely right. Frankly, I don't really care one way or the other about the ending.
Not that there isn't any good stuff in this book at all. The plot's okay, and Clark really doesn't strike me as all that terrible a kid (he certainly isn't any worse than young Woodie Smith).