I'm on a SF kick these days. I sorely miss Heinlein. Of these great 40s Sci-Fi writers (Asimov, Heinlein, Clarke, Bester), Heinlein and Bester were as smart as any of them but a lot less wooden in their prose. Their characterizations were powerful, flawed but interesting heroes in really novel situations (Bester similar, if Heilein had smoked an awful lot of opium).
His most famous novel, Stranger in a Strange Land, released in 1961 is perhaps the least similar to the rest of his catalog, and a coincidental response to the hippie movement of the time, he basically shows thoae hip kids how it would really work if they were smart enough and had time enough for Love. In a way a retelling of the story of Jesus, giving his life to lift his people up.
But his best novel is The Moon is a Harsh Mistress, a look at a thrown=together group of diverse and ordinary people making their way and their own rules and what they would do confronted by choosing between slavery and certain eventual death or revolution on the moon. Good stuff about politics, relationships, and how people react in extremis.
He was interested in war, although not a warmonger, I think. Rather, as most men of that time he feared for his country in a world that would soon have atomic bombs by the score and not a few ill-feelings for the US. Read his essays written in 1945 calling for the creating of a stronger UN that could control all the nukes and armies and prevent war everywhere. Can you imagine something like that from our own warmongering neocon chickenhawks. Self-evidently Heinlein would have little use for such as these.
And he was sexist. In those days many were (J. R. R. Tolkien was a famous one as well). Women were led, women were not very important, women were seen and not heard. To give credit where it was due, this was changing in Heinlein's work. Female characters got stronger in his later works, with some books written from a female point of view. And an entire book on the difficulties and joys of being a woman, set out carefully, fairly and lovingly in his later book I Will Fear No Evil, about a dying billionaire whose brain is transferred to the body of a young woman who he loved, and so he wished to continue the life of her exquisite body properly.
Check him out. Some of his notions about technology seem a little dated, especially in the older books, but you'll never find better war stories set in the future, or better thoughts on how we would deal with the future.