I feel like Stephen King is highly overrated as far as horror is concerned, but when it comes to sci-fi/history, he is very solid.
"11/22/63"
It is a story of a reluctant time traveler from the present day who has a portal that can be used at any time to go back to 9/9/58. When traveling, no matter how long he stays in the past, it is only 2 minutes in the present. Each time he uses the portal, it resets everything previously done. He then uses it, with the guidance of a friend, to study Lee Harvey Oswald and stop the assassination of JFK. The past does not like to be changed though, and it presents some very unique and pressing challenges along the way.
It is a very accurate portrayal of how life was lived in the 50's and 60's, even down to the lingo. He (King) did a great job thinking through the time travel scenarios to ensure everything added up and didn't leave loose ends or completely bogus story lines.
Definitely a solid read.