One of the famous astronomer's sf novels, a very short book (170 pages) featuring a contemporary 1966 world where suddenly large chunks of the Earth are sent back to different times - western and central Europe to 1917, the Balkans to classical times, other parts to who knows where. Our narrator is a musician, his friend a brilliant mathematician. Hoyle works in a lot of his own personal obsessions - mountains, classical music.
I can't help feeling that Brian Aldiss used a number of ideas from this book, especially in The Eighty-Minute Hour and Frankenstein Unbound - and the whole tone seems very Aldissian to me, much more so than the earlier The Black Cloud. Do we know how much Hoyle followed the genre, as well as contributing to it himself?