I really liked this but the reason for 3 stars is I couldn't quite wrap my head around the time travel and how the first time she leapt to 2004 there was already a letter from the previous year for her. So it seems like this is the second round of time jumps she's done.... She just doesn't have memory of the actual first time. 

I also was a little confused at what she was "supposed to learn" as this seems to be the only reason I can think of for time jumping. 

But it was fascinating, often funny and sometimes heartbreaking, but ultimately a different take on time travel stories. I enjoyed the journey though I may have wanted for a bit more.