This book contains a series of short stories about time traveller Hanville Svetz (plus two unrelated stories). Hanville Svetz lives in a future in which almost all animal life (other than humans) has become extinct. Svetz works for the Institute of Temporal Research, and travels back in time to collect animals or objects for the whim of the somewhat childish Secretary-General of the United Nations, whose position has become a hereditary monarchy.
The stories have fantasy elements, suggesting that time travel is a fantasy, and that Svetz is travelling to the world of fantasy without realising it.
Some of these stories had previously been published.
I found this a fascinating series of stories.
The Flight of the Horse (1969) [originally titled "Get a Horse!"]
In the title story of the collection, Svetz is required to travel to the past to find a horse, a task in which he succeeds, but with the interesting result that the animal he finds has a horn on its forehead.
Svetz is required to fetch the largest animal which ever lived - the sperm whale. However, the creature he finds is an even bigger sea serpent, which will not fit in the large time travel vehicle brought specially this time.
Bird in the Hand (1970)
Svetz was sent to get a roc, but returns with an ostrich. Looking at the flightless bird, he wonders if it is a neotenous species - one which remains in an immature form as adults. He asks the Palace Veterinarian to regress it to its evolutionary ancestor. And yes, it turns into a huge roc, bursts out of its enclosure, capturing the one elephant the Zoo possesses. What are they going to do about this huge ferocious bird of prey flying over the building?
In the meantime, the Secretary-General has asked for the first motor car. Zeera, a female colleague of Svetz's, is given the job of obtaining a duplicate of the first vehicle Henry Ford built. However, she makes a mistake when using the duplicating device, and removes the car from existence. With the internal combustion engine having never been put into production, the people of Svetz's time pass out, so used have they become to breathing polluted air. Svetz and Zeera must come up with a solution to return the timeline to normal.
There's a Wolf in My Time Machine (1971)
Svetz captures an arctic wolf in the past. However, the time machine's air supply malfunctions on the way home (the horse had damaged it with its horn in the first story) and he makes an emergency stop. The wolf has transformed into a half-humanoid form and starts to attack him, so he seeks refuge with some local people. He soon realises that he is in a parallel timeline, where wolves had evolved into intelligent beings. In the meantime, he is starting to revert to ape-form. He must return to his time machine as soon as possible.
Death in a Cage (1973)
On return from a trip to the past, Svetz sees a ghostly figure in his time machine. Back in his own time, his boss tells him to go back and try and capture the ghost. He travels back, and the ghost materialises into a skeletal man.
The man - Nathaniel Reynolds - is an earlier time traveller from an alternate timeline, in which the Cuban Missile Crisis erupted into nuclear war. Reynolds' skeletal appearance is due to radiation. He had been sent to change the timeline to prevent the war from happening. But then he could not return to his own time, and has been wandering through time as a ghost for ages. He now wants to change the timeline back, and threatens violence to Svetz if he does not cooperate. But will this wipe out Svetz's own timeline?
In this sequel to "The Flight of the Horse", time traveller Hanville Svetz and his two female companions Miya Thorsven and Zeera Southworth travel in both time and space, as they travel to the Mars of the past, when intelligent beings still lived there. Their space probe has shown a giant tree - the Hangtree, or Beanstalk - extending from the surface of Mars to orbit, and the team are sent there to get its seeds, to enable Earth to grow a similar tree to use as an orbital tether - a cheap method of transfer to orbit. Hanville and Miya become separated from Zeera who is piloting the spacecraft, and undergo a number of difficulties, exploring the tree for seeds, coming into conflict with the various Martian species, difficulty finding food and travelling across country to rejoin Zeera at the spacecraft. There are more adventures when they eventually return to Earth.
Niven has borrowed ideas about Mars from various authors, most notably Edgar Rice Burroughs, and built on the idea of the canals on Mars as observed by early astronomers. He has also incorporated several myths of giant trees, such as the Norse Yggdrasil, as well as giving an explanation for the origin of the "Jack and the Beanstalk" story.
Like "The Flight of the Horse", this story is not serious science fiction, but makes use of ideas from fantasy, myth and early science fiction, which adds to the enjoyment of the story.