At one time, I listed this as one of my favorite SF books. Reading it again after 50 years, I can see why. Mainly because of two stories, the title one and "The Long Watch."
When I was a teenager, I wanted more than just about anything to be a poet. I loved all kinds of poems, and of course I wrote my own. (Little known fact: my first national publication was a poem in a magazine called The Runner, and I published poems in a few "little" magazines, too. Not to mention one in Grit.) So it's no wonder that I loved "The Green Hills of Earth," the story of Rhysling, the Blind Singer of the Spaceways. I loved Rhysling's poems, too, and I'm sure I wrote more than one in painful imitation of them.
"The Long Watch" undoubtedly appealed to me for another reason. I admired the protagonist's sacrifice to prevent a military coup, and I still get a sentimental thrill out of this paragraph: He was not alone; there were comrades with him -- the boy with his finger in the dike, Colonel Bowie, too ill to move but insisting that he be carried across the line, the dying Captain of the Chesapeake, still with deathless challenge on his lips, Roger Young peering into the gloom. They gathered about him in the dusky bomb room. Even as a kid, I knew I could never be a hero, not that kind, but it was great to read about one and pretend for a little while that I might be.
The other stories are still fun to read, if not quite as wonderful as I thought they were 50 years ago. They might not even be among Heinlein's best. But I recommend them highly. This is what SF was all about at one time, at least for me.