I'm not really sure what it was about this book, but most of it rubbed me the wrong way. Granted, the prose is okay (not Heinlein's best however), but the story is too moralising (and often taking the opposite side I would choose - "an armed society is a polite society"? ), parts of the plot are bizarre, and as another reviewer pointed out, the last third of the book drags on with philosophising that doesn't seem to go anywhere (at least, not anywhere interesting). Certainly sub-par for Heinlein, both in the science and in the plot-line.