A World Out of Time by Larry Niven is a book I first read in my early twenties. Since then I have re-read it many times. It is a story that can truly expand the imagination of the reader with its breath-taking imagery and scope.
Not in the least disjointed, this far-reaching tale has a tightly coherent and complex plot. It reaches out into a future where humanity has lost its way, having fought over and forgotten its very purpose. Wholly believable characters and vivid description bring the story to life.
Niven shows us a world, its advanced but decaying technology and its splintered culture in detail you can almost touch.
Riveting - a real page-turner, with the hero moving from one desperate scrape to another, as different factions rival each other to pry from him a secret even he does not know he has.
Full of ideas, inspiration and intelligence, this is my outright number one SF novel of all time.