Off topic? Probably.

I just sent the movie, Primer back to Netflix, after watching it three times, and reading a Wikipedia article on it. It is a great, artful, time travel movie. However, the plot was very hard to follow the first time through, and by the second time more details fell into place. I really needed to read the Wikipedia explanation of the plot before it all came together for me. One of my favorite parts of the movie involves the two main characters Abe and Aaron traveling backward in time in two boxes they have constructed. The box allows you to ride in it backward until you get to the time when the box was originally turned on. You see Abe stumble out of his Box, and then after a few seconds Aaron stumbles out of his. Abe says to Aaron that he got out of the box too soon! Hee hee. This is the sort of detail that is missed by most time travel movies I have seen, and these things tend to get muddled in books as well.

There are two basic approaches to Time Travel, which I will whimsically refer to as the "Back to the Future" approach, and the
"Twelve Monkeys" approach. In the former, it is possible to go back and change the past. You will not read about yourself in a history book before leaving on your journey. Time travel makes changes to the time line possible. This is probably the most confusing type of time travel, and is exactly the sort of thing that happens in Primer. The "Twelve Monkeys" approach holds that you cannot change the past because it's already happened. Thus you could read about yourself appearing in a time machine in a newspaper from 5 years ago before you actually do it. There is a wonderful short story, "By His Bootstraps," by Robert Heinlein that explores this theme.