One of my favorite time travel novels is 'The Big Time' by Fritz Leiber.
The two big ideas in the book. First, that there's a Law of Conservation of Reality. Go back in time and shoot Hitler. He dies. Then gets better, really fast. Twenty minutes after you shoot him, he's fine. Spend your whole life shooting him and the history books will just ignore it. It takes an army of time travelers working night and day to get any changes to stick.
Second idea. There are two armies, both trying to change the past/future. They have been at it since before the Big Bang and will go on until the Heat Death of the Universe. They recruit humans but no human has ever seen the big bosses, just low ranking stooges.
And the second one reminds of the TV series "Travelers", with future factions of time travelers emerging from the changes of previous time travelers in the past. It's worth noticing that time travelers from "Travelers" only displaces their mind consciousnesses, not their entire bodies.
That's an unusual take on it. That would definitely have been recorded somewhere as a miraculous recovery. Usually it's written that the time travelling assassin fails in such a way that no-one notices, and if they do have some kind of effect, generally ends up being the cause of the history they were taught rather than the changer of it.
The author did a few stories based on the 'Change War.'
In one, a time traveler goes back and takes the bullets out of a gun, hoping to prevent a death. There's no gunshot, but the victim is hit by a meteor and dies anyway. The idea is that Time is immutable and almost impossible to change with only one set of hands.
. It takes an army of time travelers working night and day to get any changes to stick.
Changes do occur in the story. The participants talk about the 'Change Winds' and how people can just disappear because thier timeline has been shifted and their parents never met.
Ctrl+F Hitler, ah, there it is. I feel like the xkcd comic missed an opportunity to have a 1932-1945 segment in there about the biggest cause of death for time travelers being OTHER time travelers killing them before they can successfully go back in time and kill Hitler, lol.
Re: conservation of reality, I feel like if I went back and shot Hitler, I would miss, or be stopped by security, or bad weather, or my gun would misfire, or even if I managed to actually do it, he'd be replaced by a look alike, and then it would turn out the guy we always thought was Hitler was actually just an actor, or something. Like if someone went back and killed baby Adolph when he was six months old, the parents would adopt another kid and name IT adolph, and there you go. Whatever happened happened and can't be undone, not through magic resuscitation of a corpse, but through smooth and natural intervention of reality itself, if that makes sense..