Book 60: "Roofworld" by Christopher Fowler

The night was clear and cool and Rose was alone on the rooftops of London. It seemed peaceful to be above the city and yet still be a part of it. Carefully, she lined her camera up to the ledge along the building and looked through her viewfinder once more. But this time, instead of seeing the empty roofscape of the city, she saw the strangest thing. Running figures, some loping, some as if swinging on invisible ropes, bounding and leaping across the angled rooftops on the other side of the street. there were perhaps fifteen of them, young, old, men or women, it was difficult to tell. there was even a dog of some kind, darting silently between their feet.

Since the 1920s the rooftops of London have been home to a well-organised society. Hundreds of people at a time have lived up there in secret, travelling along cables that they had strung between the buildings. But now, their world is crumbling around them as they fight for survival against the evil Chymes and his gang, while down below the police are starting to wonder what is going on, when several dead bodies are found that seem to have been killed up above. This book is set in the late 1980s. and even then the inhabitants of Roofworld were seeing more security cameras appearing on the rooftops. I'm not sure that the story would be feasible if it was set nowadays with so many CCTV cameras everywhere. People may not look upwards, but the cameras see everything.

Book 61: "Not Before Time" by John Brunner

Visiting hours, naturally, had to be based on local - Earthside - time, but it was no help to anyone when those who came were confronted with a series of inert lumps, even if those lumps were fifty lightyears from home.
Attempts were consequently always made to adapt the aliens to a twenty-four-hour day. Some adjusted easily; others could not at any price, being too tightly fixated on their home world's night-day cycle.
During the ten hours of the day when the zoo was open for visitors, as many as half the exhibits might be slumbrously dull. Alternatively, the cycles might chime together and the whole place become a buzz of vigorous movement, colour and sound. The latter occasions always brought visitors in hordes because they were always well advertised. for convenience they had to have a name and a definition: a Coincidence Day was one where forty or more of the fifty presentations were at day activity peak for at least five hours.

A book of science fiction short stories first published in 1968. My favourite was "Coincidence Day" which was about an zoo of extraterrestrial species on Earth. I also liked "A Better Mousetrap", "Seizure" and "Treason, but overall I prefer this author's novels to his short stories.