Here is it, my first Heinlein! This was a really fun novel and I loved it. We may see some Heinlein-collecting in my future.
Kip is your average high-school kid, except that he is extra-attached to his ambition to go to the Moon. He enters a soap slogan contest, and while he doesn't win the first prize of a Moon trip, he does win a used spacesuit, and he spends a summer fixing it up just right and learning his way around the engineering. While taking it out for one last walk, he's suddenly kidnapped by space pirates! His fellow prisoners are Peewee, a pre-teen girl a little too smart for her own good, and the Mother Thing, an alien. They've got to escape and warn Earth about an imminent invasion, but all they've got to work with is their own brains.
This is a great adventure story for older kids and YA. Kip and Peewee are both inventive and self-reliant, but they're also kids. Peewee in particular has that blend of smarts and blind spots that is typical for a child that age, while Kip is not as clever, but has more common sense and experience because he's older. There are two interesting alien species with differing societies and goals, good stuff. The whole thing is a three-stage adventure that gets bigger, with more at stake, every time.
Heinlein wrote this in 1958, and so Kip has a slide rule and no electronics. I didn't feel that the story had really aged, though. It's nice that he doesn't have an iPhone to rely on for calculations--he has to do them in his head--and he only mentions his "slipstick," left at home, a couple of times in passing. Really, you'd have to be quite a nitpicker to complain about the age of the story, because it hardly feels dated at all.
My 14-year old read it too and now she wants to read more. I think we are both going to enjoy our new author.