A thought-provoking book. Matheson obviously considered the psychology behind it long and hard because it’s very realistic. It had the potential to be quite a boring book (same routine over and over), but I think that realism saved it.
I don’t read a lot of horror because I have an overactive imagination. I know technically this is more like science fiction, however I’d argue it had horror elements in it. Yet even so, I didn’t find it scary and I liked it all the more for that. The style flowed well, even without a lot of dialogue and I can certainly see why Matheson is well respected in the field of speculative fiction.
I found the ending (the last two parts) a little unexpected, but overall quite apt. I felt it revealed even more than what came before of the ideas underlying this. I suppose the best speculative fiction (or at least a lot of the early-ish stuff) are always parables, just like this one could be considered to be.