Wyndham had a reputation for writing "cozy catastrophes" and of the books that I have read this one most lives up to its reputation for that. The plot concerns aliens impregnating an entire English village full of women. It is clear to everyone what's taken place and there is a certain amount of freaking out about it, but it all is considerably less than one would expect. Instead, there is an absurdly English, lets ignore the implications to the whole thing.
The book lends itself to parody. One can imagine a scene where everyone is sitting around having tea and cucumber sandwiches where the Butler says "I'm afraid sir, that aliens seem to have impregnated your wife." "I say Jeeves. That's really not on." Anyway, so far as I know this is the first aliens impregnate women with their babies book and deserves a lot of credit for that. It's fairly well written. It also has a view of evolution in which humans have no special place and will eventually be out competed. That view has been in every Wyndham book I've read, and while he's far from being the only science fiction author to write about it, I now think of it as his signature thing.
Overall good, but would be a lot better, if people reacted a little bit more plausibly to their alien babies, or if they were mind controlled to not know they were alien babies or something.