Mark Lawson wrote a decent 'Waht if...' novel based on the premise that JFK wasn't killed in Dallas... it was called Idlewild, as the airport never had to change its name to honour an assassinated Prez.
If you ever see red dwarf back on tv look out for the episode where they travel back in time for a curry and accidently stop JFK being shot then take him back in time to kill himself from the grassy knoll. Priceless!