I forget where I heard it, but I'm pretty sure that after all the novellas are released, it'll be up for purchase as a single volume. It's doubtful that the story itself was really meant to be exclusive to backers anyway - our reward was just free copies of the novellas as they're written, rather than waiting for it all to be finished.
I don't know any details on when or where to get it though, but I'd guess either directly through HBS or Catalyst Game Labs, which handles all the other BT fiction. Hopefully somebody else here has better information?