This is perhaps the best time-travel novel ever written. The episodic pastiche of Billy Pilgrim's life is very carefully constructed, and Vonnegut's prose flows with deceptive ease. When I first read this (in high-school), I didn't recognize the references to Vonnegut's other books, but several characters have cameos, including Kilgore Trout (of course), Eliot Rosewater, Howard Campbell, and the city of Ilium. There may even be others, but I haven't read all of Vonnegut's novels yet, and I may have missed some.