Then I glanced at the ring on my finger.
The Snake That Eats Its Own Tail, Forever and Ever. I know where I came from - but where did all you zombies come from?
I felt a headache coming on, but a headache powder is one thing I do not take. I did once - and you all went away.
So I crawled into bed and whistled out the light.
You aren't really there at all. There isn't anybody but me - Jane - here alone in the dark.
I miss you dreadfully!
That's one of the weirdest endings ever. (That reminds me of all the cults that were forming at the time around around lesser sci-fi writers, such as L. Ron Hubbard and Ayn Rand. There was something in the air in the run-up to the Sixties. It speaks to Heinlein's strength of character and/or short attention span that, despite his tendency toward solipsism that runs amok in 1961's Stranger in a Strange Land, he was less tempted than they were to give in to being a cult leader. Heinlein had the ego, but not the capacity for boredom.)
I was thinking that maybe Bradbury's changeable history makes for better comedy and Heinlein's deterministic history makes for better tragedy, but perhaps the opposite is true. The gyrations that a Heinleinian time travel plot has to go through to make everything wind up being the same are often exhilaratingly comic, while Bradburyesque plots like the new Looper, which takes a strong stand at the end in favor of [Spoiler Alert!] mother love, often tend toward the sentimental.