This short novel (almost a novella really) explores the paradoxes which would be caused by an individual being able to travel through time. Daniel is a young man who receives an inheritance from his uncle Jim which is a timebelt which enables him to travel forward or backward any span of time, or to skim backwards or forwards observing developments as an outsider. He begins with the bog standard wheeze of going forward to find out the results of future horse races and then placing bets on the winners in the present, and this part of the novel is amusing. But then he goes on to more expansive and dramatic changes, interacting with multiple versions of himself, and the novel ceases to have much of a plot, and becomes a concept novel about the paradoxes he faces and the alternate timelines he invariably creates every time he jumps anywhere. While I have always been fascinated by the concept of time travel, the presentation here didn't work for me and became rather repetitive, and I wasn't satisfied with some of the reasoning, e.g. that the first action of the owner of the timebelt should to erase the timeline in which it was created so no one else could have one - but wouldn't that mean the owner didn't either? So ultimately I don't think was as effective as it could be.
This novel was originally published in 1973 and Daniel came originally from 1975. The edition I read was updated by the author in 2003 and set in 2005, but the only differences to the text that I noticed were references to 9/11 and compact disks, which initially baffled me given the novel's age.