I was able to score a copy of this book a while back an have slowly been making my way though it -

The general idea is that you are a time traveler. You can hop around through time with a group of other time travelers and you try to do ... something. Haven't really gotten that far.
What made me pick this up was a discreption that I read of someones first time playing it. The group had just become time travelers and they had a mentor. The mentor left a note in the refrigerator telling them to make him a sandwich. The fridge was empty. It was night and all the stores were closed. One of the players decides to hop backwards in time, go to the store, and buy supplies. He then goes to the house, while in the past (I don't think you can carry a bunch of stuff with you while you travel through time) and put the groceries in the fridge and took out the note. He then traveled back to the 'present' with the rest of the party to make a sandwich.
Here is where things get interesting.
Since he took the note out in the past, it wasn't there in the present to let them know they needed to make a sandwich, so he wouldn't have gone back in time. He had created a paradox. This is handled mechanically by your character getting fragged (not exploded ala doom, it is a numeric rating to how unstable you have become.) In order to rectify this the player had to travel further back in time than he had originally traveled to set things in place that would let him know not to remove the note.
That just pulled me in right there.
I haven't made it very far through the book but it has been pretty interesting so far.