Stranger in a Strange Land has what so many people object to in Heinlein in what was probably its most concentrated form up to that point: his didactic side. It runs throughout all of his work, but at this point it began to become a major part of any book he wrote. Personally, I don't mind this, as it's expressed in terms fitting to each character and is often done in exaggerated form, to gig the reader into thinking through things. No, not all of what's expressed in Stranger represents Heinlein's own views -- far from it. But he wanted to get people talking and thinking about things that had simply become so much accepted that anyone disagreeing tended to be rather squelched; Heinlein, being very pro-free speech, was adamantly against that sort of stultification.
As for Starship Troopers: Action? What action? Except for the very opening and the last chapter, action is at a bare minimum here; it's concept, and a mental bildungsroman, he's concerned with, not with "physical" adventure, as it were, more mental adventure, the adventure of growth as seen through use of a character's changing ideas. Yes, these are "preachy" books, and I'm fully aware of their flaws -- which, by the way, are not those of being preachy, as this is a recognized branch of literature, the didactic novel, with its own traditions and requirements -- but because there's some slipshod writing here and there in the novels themselves. Nonetheless, the books challenged me at different points in my life, and because of that, I learned to think things out more clearly; and for that I owe Heinlein a debt. The use of a character rather than just straightforward arguments make it somewhat more accessible to the majority of readers; and the fact that these books have never been out of print since they were published, indicates that this technique works for a great many people. There's nothing wrong with disliking the books, but these are by no means bad books; flawed (at times rather seriously so), but what they were intended to do, they do quite well.
One final note. On the subject of women having trouble with these books. The majority of women I know who have read Stranger have all been big fans of the book, while having serious problems with, for instance, Starship Troopers, despite the fact that you have some very strong women in the latter, and he makes it plain that there are certain abilities and strengths in which men simply can't compete with women. Perhaps this is a regional thing; I don't know. But it certainly doesn't put off all women; the ones I've met who didn't like it were the traditional "housewife" sort, who were against Women's Lib, etc., not the ones who supported equality. It would be interesting to know if this is a regional response, or whether it crosses such boundaries, but that's for the patient scholars of the sf foundation to look into. I'd just say that I don't find it to have repulsed very many.
