The Sirens Of Titan

When Winston Niles Rumfoord flies his spacecraft into a chronosynclastic infundibulum he is converted into pure energy, and only materializes when his waveforms intercept Earth or some other planet. As a result, he only gets home to Newport, Rhode Island, once every 59 days, and then only for an hour. But at least, he now knows everything that has ever happened or that will ever happen.