Ursula has written many famous books whose endings will change the way you think. One of her lesser known works has a hidden message which you can find here: https://mega.nz/#!jaRQXKbS!QkdIFePvAMwazGnSAoq6exbpAC_FrRltI0V2cf4TPLU
Hint: RFC 4648 :)
Also that the start of the text up:
As the truck lurched over a bridge across the Nenana River
There are at least two chapters and that from that text it changes... but besides those two things, I am unable to see anything else, any clues...