Stranger in a Strange Land belongs to the second sort of Heinlein novels. The first sort are wonderful stories about human resolve and conquering the future. The second sort are... well, I can't get through them.
Check your local used bookstore. Not a lot of Heinlein but you can usually find one or two. Or the bookstore. In general, look for a publication date in the 40s and 50s, most of his best stuff was written then. As an adult, I would recommend "Moon is a Harsh Mistress", "Double Star", "The Door Into Summer", and "Starship Troopers" as starters. The juveniles are wonderful but best if you either already like Heinlein, or encountered them in middle school.
If I take twenty years off to raise them, my training is worthless, but the other message of "Podkayne of Mars" is that if you have kids, you'd darn well better raise them.
I'll be check Poka out too. I commend this kind of attitude ... save for the part where the training is "worthless" simply because it takes at least 10-15 years to get a brood to fulltime schoolage.
I think a lot of women realize too late that ANYONE could have fulfilled their stinkin' career job as well or better than they but that it's not so easy to pop out according to Daytimer Plan the kids they figured on having once the More Important things in their life were established.
Women who worry that their training might become worthless if they have kids should just have themselves sterilized and be done with it. I feel sorry for children-as-desk-accessories. I find it pathetic and depressing in the extreme to hear the daily phone calls and the oft-repeated: "But Mommy's got to work -- along with Daddy the doctor -- so you can HAVE [insert anything but a fulltime Mom here]."