Time Patrol is a collection of short pieces by Poul Anderson centered around Manse Everard, a World War II vet whose life changes when he answers an ad by Engineering Studies Company promising a job with high pay and foreign travel. The travel turns out to be up and down the timeline, policing those who want to remake history. It needs doing because upon returning to twentieth-century New York from a skiing trip to the Pleistocene (where else better?), he finds everyone speaking Irish (don’t they, already?).
The stories, published over four decades from 1955 to 1995, strike me as profoundly conservative. One analyst has called them anti-alternate history. Any attempt to clean up the blood of history creates a new wound. Bad as it is, we already live in the best of possible worlds, and any attempt to change it is bound to make it worse. Everard’s adventures through time are filled with loss for him, his fellow officers, and the benighted residents of the unchangeable past.
Anderson is genuinely interested in the historical epochs he describes and is careful with the details of his settings. However, he does not care much about the possible science and technology related to time travel. Everard gets to the past on a bicycle-like machine in homage to H. G. Wells. ( )

Manse Everard es un patrullero del tiempo, uno de los esforzados paladines que protegen la historia de las alteraciones que una máquina temporal podría introducir en la incierta matriz del futuro. Reunidas por primera vez todas sus aventuras en un solo volumen, le vemos intrigando entre los persas, con los conquistadores españoles, en la Germania invadida por Roma y en otros muchos momentos cruciales de la historia.

The complete novella/short story cycle in one volume. I don't agree that time has only one shape, as the author contends, but rather that his posited Danellian posthumans are manipulating all the eras before to make sure they are the only possible result of evolution. But whatever, I loved the clarity and plausibility of this vision of human time travel's likely results. ( )

Sample Chapters: http://webscriptions.net/chapters/1416509356/1416509356.htm