11.22.63 by Stephen King. King is a master storyteller. With access to 1958 surely you'd want to prevent an event that shocked the world and changed the course of world history; the assassination of JFK. Teacher Jake Epping tries to change the past but it is obdurate and refuses to change with horrific consequences. Part sci-fi, part historical fiction, this is actually a love story for a simpler time and for Jake as he finds love in the past. Lengthy but brilliantly researched and gripping.
Part memoir, part confessional, part treatise on the isolation of childhood, interspersed with dreamy intellectual reflections on the early videogames that shaped his life (all of which I have played) this is wonderfully written and moving.