I published one a long time ago but I haven't started writing it yet.
Hi,
Have you written a time travel book? If so what process did you follow, what happened and how did the book turnout?
I have started several books, but then again my total list of WIP is insane. That said, I consider myself the sort of nut job that likes to just sit around and discuss the limitless possibilities of time travel, temporal etiquette, and its spin-off the Many Worlds Interpretation.
In role-playing games I have used time travel as an element more than once and I think the use of it there is very similar to its use in writing in general.
The main trick is to decide when each destination is, and what could go wrong in each era. Seriously, if you're not prepared for the worst, you won't be able to write the story as things go the way you want. The quickest way to get enthusiastic readers up in arms with a time travel story is to have one of your characters do something in the past (even something innocent) and the side effects of that incident are not explored. Any change can spiral out of control, depending on which rules of Temporal Theory you use.)
Example from a book I was working on:
My MC travelled from his post-apocalyptic time period to late 20th New York City. He was familiar with the period (long story) and new he could blend in easily. However, in the course of this, the MC bumped a total stranger on the street. The two of them got into a very brief shouting match about who was at fault. Not more than 5 minutes.
What ultimately came to light was that the guy the MC bumped was actually supposed to be one of the crazies that nearly destroyed the world in the near future, creating the post-apocalyptic society the MC had just left. Because of that 5 minute delay, this guy missed meeting one of his future fellow crazies and thus didn't get recruited into the plot. The guy they hired instead was a hundred times crazier and the already awful apocalypse was made worse, resulting in the utter destruction of the world.
Enter the paradox: If things end in the early 21st century then there is not post-apocalyptic society for the MC to be living in during the 35th century. So he can't go back in time...so he can't bump into the guy...so that guy is hired...so the world is still ravaged but not destroyed...so then there is a society afterwards...so the MC can be there...so he can go back to the 20th... See the idea? This creates the nasty word "paradox" and again depending on the temporal theory you want to use, reality simply unravels itself and creation ceases to exist.