As with many of David Brins works, this novel is set on a highly imaginitive and detailed future. The core concept is that people can make copies of themselves. These copies only last for 1 day and their thoughts and experiences can be 'inloaded' by the real person before the 'dittos' dissolve. This is a lighthearted piece, but it also makes some interesting philosophical and metaphysical points re the nature of self. The plot revolves around the investigative work of a private detective and this allows him to both explore and explain the world around him. There are a few plot devices..copies can't make copies; copies are not exact duplicates but can be enhanced or detracted from (for instance to make them more able to study or even to be more obedient) There is a large touch of the Philip Jose Farmers about the novel though, particularly as the various plot threads come back together for the final denouemen. My main complaint being the levels of deux ex machinery, which I found a little hard to swallow. In conclusion. I noticed that one of the other reviewers mentions 'The Practice Effect' and I'd agree that they are similar works. Both start with an interesting premise, but have a relatively slight plot and neither quite live up to what I would regard as the mainstream SF works that DB has written (that is his The Uplift novels). Worth reading, but not Mr Brins best work.