Well, there are actually two errors in that sentence. First, John Wyndham was actually not named "John Wyndham" but John Wyndham Parkes Lucas Beynon Harris. Second, they were not all the books written by that gentleman. He wrote others under other names. He even co-wrote a book as a collaboration between John Wyndham (that is, himself) and Lucas Parkes (himself).
The books have much to recommend them. They were written in a clear and understated style which, in several books, contrasts with an apocalyptic or post-apocalyptic setting. One of them, The Chrysalids, is one of the few science fiction novels I've read set in Canada (though Newfoundland had, in fact, been part of Canada for only six years when the book was published in 1955).
Several films have been made of his books. The best is the The Village of the Damned (1960), which captures the mood of the book it is based on, The Midwich Cuckoos. Other books of the time had a similar theme (A for Andromeda, for example), but the Wyndham treatment provides interesting characters and a genuine moral dilemma.
It also spun off a movie sequel, Children of the Damned, in 1963.
John Carpenter remade the original film in 1995. Why he thought he could do better, I don't know. His version has won a Golden Raspberry award for the worst remake. Be warned, unless you are a completist fan of John Carpenter, Christopher Reeve, or Kirstie Alley movies.
Other John Wyndham books have been adapted into films or television series: The Day of the Triffids and Chocky among them.
Years after I bought the collection of Wyndham books, a new Wyndham appeared in the bookstores. This was Web (1979). Apparently its publication had been held up for ten years by Wyndham's estate, due to a copyright dispute. The plot and setting are different, but as in Wyndham's short story "Wild Flower" (in The Seeds of Time), a desire for a natural, utopian existence confronts the legacy of atomic technology. In one story, natural mutations provide hope for a better future (as they also do in The Chrysalids); in the other, they create a nightmare and promise a greater nightmare in the future.
Now, I discover that there is another John Wyndham book, Plan for Chaos, published in 2009, forty years after Wyndham's death, by Liverpool University Press and Penguin Books. He wrote it at the same time that he was working on his first "John Wyndham" novel, the The Day of the Triffids. It was unpublished because of the decisions of publishers, not the judgement of the author. Consequently, no book featuring resurgent Nazis and cloning found its audience until 1979, when Ira Levin published The Boys from Brazil. The Wyndham book, however, adds two ingredients that the Levin book does not, Nazi flying saucers and matriarchy. The book was, perhaps, a little ahead of its time, so it sat with his papers until they were sold to the University of Liverpool.
An expanded and corrected introduction to Plan for Chaos is on the Hubub blog. I need to look at it again after I re-read some of the other John Wyndham books, because it makes statements about plot points in them that contradict my memory. To quote the theme song from the tv show Monk again, "I may be wrong (but I don't think so)."